Torque sensor used for robot arm, has an exertion support body exerting the torque to an annular deformation body

ABSTRACT

A torque sensor including an annular deformation body disposed so as to surround a circumference of a rotation axis, an exertion support body, a fixing support body, and a detection circuit. The annular deformation body has four coupling parts, and four detection parts positioned between two coupling parts which are adjacent in the circumferential direction of the annular deformation body, the detection parts undergoing elastic deformation by exertion of torque. The detection parts each are formed in a convex shape on one side in a direction along the rotation axis and are formed in a concave shape on the other side in a direction along the rotation axis. The detection circuit outputs electric signals on the basis of elastic deformation undergone to the detection part of the annular deformation body.

RELATED APPLICATION

This application is a divisional of application Ser. No. 15/546,605filed on Jul. 26, 2017, which is an application under 35 U.S.C. 371 ofInternational Application No. JP/2015/052783 filed on Jan. 26, 2015, theentire contents of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a torque sensor and in particular to asensor having functions to output torque exerted around a predeterminedrotation axis as an electric signal.

BACKGROUND ART

Torque sensors for detecting torque exerted around a predeterminedrotation axis have been widely used in a variety of transport machinesand industrial machines. For example, in Patent Document 1 given below,there is disclosed a torque sensor of a type in which mechanicaldeformation caused by exertion of torque is detected by a strain gauge.Further, in Patent Document 2, there is disclosed a sensor for detectingtorque exerted on a shaft by forming a magnetostrictive film throughplating on the shaft surface and measuring a change in magneticproperties of the magnetostrictive film. Still further, in PatentDocument 3, there is disclosed a torque sensor of a type in which amagnetism generating part is provided at an end portion of a torsionbar, and a change in magnetic flux density of magnetism generated by themagnetism generating part is detected by use of a magnetic fluxcollecting ring. In Patent Document 4, there is disclosed a torquesensor of a type in which a large number of magnets are disposed in acylindrical shape so that the N poles and the S poles are lined upalternately in the circumferential direction and magnetic fieldsgenerated by these magnets are detected.

On the other hand, there is also proposed a torque sensor in which theshape of an annular member is deformed by exertion of torque to detectelectrically a mode of the deformation. For example, in Patent Document5, there is disclosed a torque sensor for which a link mechanism fordeforming in a radial direction the shape of an annular member byexertion of torque is prepared and in which a force applied in theradial direction is detected by a load sensor on the basis ofdeformation of the annular member. In Patent Document 6, there isdisclosed a torque sensor in which strain gauges are used to detect anexpansion-contraction state of each part of an annular member.

Further, for example, in Patent Documents 7 and 8, there is disclosed amethod for using a capacitive element as a unit for electricallydetecting displacement occurring at each part of a structural body. Acapacitive element can be constituted of a pair of opposing electrodes,and a distance between both electrodes can be detected as a capacitancevalue. Therefore, it is suitable for a displacement detection unitprovided on a sensor. Thus, in Patent Document 9, there is proposed atorque sensor in which the shape of an annular member is deformed byexertion of torque to detect displacement at each part resulting fromthe deformation by using a capacitive element.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2009-058388

Patent Document 2: Japanese Unexamined Patent Application PublicationNo. 2007-024641

Patent Document 3: Japanese Unexamined Patent Application PublicationNo. 2009-244134

Patent Document 4: Japanese Unexamined Patent Application PublicationNo. 2006-292423

Patent Document 5: Japanese Unexamined Patent Application PublicationNo. 2000-019035

Patent Document 6: Japanese Unexamined Patent Application PublicationNo. S-63-075633

Patent Document 7: Japanese Unexamined Patent Application PublicationNo. 2009-210441

Patent Document 8: Japanese Unexamined Patent Application PublicationNo. H-05-312659

Patent Document 9: WO2012/018031

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In industry, there is a demand for a small-sized torque sensor havinghigh rigidity and a simple structure. In particular, in industrialequipment for performing automatic assembly by use of a robot arm, it isessential to monitor a force generated at the leading end of the arm andcontrol the force. For attaining such a torque feedback-type controlstably, it is necessary to secure high-speed responsiveness of signalprocessing from an electrical point of view and also secure highrigidity of a sensor structural body from a mechanical point of view.

From the above-described point of view, the torque sensor disclosed inPatent Document 9 described above (hereinafter, in the presentapplication, referred to as “the torque sensor of the priorapplication”) demonstrates performance as a sensor that is small in sizeand high in rigidity. In the torque sensor of the prior application, apredetermined point of an annular deformation body which causes elasticdeformation is supported by support bodies disposed on both left andright sides. Next, there is adopted a method for detecting deformationcaused in the annular deformation body in the radial direction as achange in capacitance value of a capacitive element. Specifically, thereis adopted a structure in which one of the electrodes (a displacementelectrode) which constitutes the capacitive element is formed on aninner surface or an outer surface of the annular deformation body, andthe other of the electrodes (a fixed electrode) which opposes thereto isfixed to the support body.

It is, therefore, possible to provide a torque sensor which is small insize, high in rigidity and simple in structure.

However, in the torque sensor of the prior application, the displacementelectrode can be satisfactorily formed on the inner surface or the outersurface of the annular deformation body, whereas the fixed electrode isrequired to be supported and fixed at a position which opposes thedisplacement electrode. Therefore, the fixed electrode is inevitablymade complicated in structure. In addition, a relative position of thefixed electrode in relation to the displacement electrode is a seriousfactor which affects detection accuracy. Thus, great work load is neededin adjusting a position of the fixed electrode. In particular, where aplurality of capacitive elements are disposed so as to be keptsymmetrical and these are used to perform difference detection, suchadjustment is necessary that an opposing electrode is made parallelthereto at each of individual capacitive elements and an electrodeinterval between the plurality of capacitive elements is also madeequal. Therefore, in terms of commercial use, there poses such a problemthat production efficiency is decreased to raise costs.

Therefore, an object of the present invention is to provide a torquesensor which is small in size, high in rigidity and capable of realizinghigh production efficiency.

Means for Solving the Problems

(1) According to a first aspect of the present invention, in a torquesensor which detects torque around a predetermined rotation axis,

the torque sensor comprising:

an annular deformation body which extends along a basic annular channelwhen the basic annular channel is defined on a basic plane orthogonal tothe rotation axis so as to surround a circumference of the rotationaxis;

a left side support body which is disposed at a position adjacent to theleft side of the annular deformation body, when viewed from a referenceobservation direction in which the rotation axis gives a horizontal lineextending laterally;

a right side support body which is disposed at a position adjacent tothe right side of the annular deformation body, when viewed from thereference observation direction;

left side connection members which connect left side connection pointson the left side surface of the annular deformation body with the leftside support body;

right side connection members which connect right side connection pointson the right side surface of the annular deformation body with the rightside support body;

a capacitive element which is constituted of a displacement electrodefixed at a predetermined position of the right side surface of theannular deformation body and a fixed electrode which is fixed at aposition of the right side support body which opposes the displacementelectrode; and

detection circuits which output electric signals indicating torquearound the rotation axis exerted on one of the left side support bodyand of the right side support body in a state that a load is applied tothe other on the basis of fluctuation in capacitance value of thecapacitive element; wherein

the annular deformation body is provided with a detection partpositioned at a detection point defined on the basic annular channel anda coupling part connected to both ends of the detection part,

the detection part is provided with a first deformation part whichundergoes elastic deformation by exertion of torque which is to bedetected, a second deformation part which undergoes elastic deformationby exertion of torque to be detected and a displacement part whichundergoes displacement resulting from elastic deformation of the firstdeformation part and the second deformation part,

an external end of the first deformation part is connected to a couplingpart adjacent thereto, while an internal end of the first deformationpart is connected to the displacement part, and an external end of thesecond deformation part is connected to a coupling part adjacentthereto, while an internal end of the second deformation part isconnected to the displacement part,

the displacement electrode is fixed at a position of the displacementpart which opposes the right side support body, and

the left side connection points and the right side connection points aredisposed at the coupling part, orthogonal projection images of the leftside connection points on the basic plane and orthogonal projectionimages of the right side connection points on the basic plane are formedat mutually different positions.

(2) According to a second aspect of the present invention, in the torquesensor due to the aforementioned first aspect,

n number (n≥2) of a plurality of detection points are defined on thebasic annular channel, the detection parts are positioned at therespective detection points, and the annular deformation body isconstituted by disposing alternately n number of the detection parts andn number of the coupling parts along the basic annular channel.

(3) According to a third aspect of the present invention, in the torquesensor due to the aforementioned second aspect,

n even number (n≥2) of the detection points are defined on the basicannular channel, the detection parts are positioned at the respectivedetection points, and the annular deformation body is constituted bydisposing alternately n number of the detection parts and n number ofthe coupling parts along the basic annular channel.

(4) According to a fourth aspect of the present invention, in the torquesensor due to the aforementioned third aspect,

when n even number of the coupling parts are numbered sequentially alongthe basic annular channel, the right side connection points are disposedat odd-numbered coupling parts, and the left side connection points aredisposed at even-numbered coupling parts.

(5) According to a fifth aspect of the present invention, in the torquesensor due to the aforementioned fourth aspect,

n is set to be equal to 2, by which the annular deformation body isconstituted by disposing individual parts in the order of a firstcoupling part, a first detection part, a second coupling part and asecond detection part along the basic annular channel, and a right sideconnection point is disposed at the first coupling part, and a left sideconnection point is disposed at the second coupling part.

(6) According to a sixth aspect of the present invention, in the torquesensor due to the aforementioned fourth aspect,

n is set to be equal to 4, by which the annular deformation body isconstituted by disposing individual parts in the order of a firstcoupling part, a first detection part, a second coupling part, a seconddetection part, a third coupling part, a third detection part, a fourthcoupling part and a fourth detection part along the basic annularchannel, a first right side connection point is disposed at the firstcoupling part, a first left side connection point is disposed at thesecond coupling part, a second right side connection point is disposedat the third coupling part and a second left side connection point isdisposed at the fourth coupling part,

left side connection members include a first left side connection memberfor connecting the first left side connection point with the left sidesupport body and a second left side connection member for connecting thesecond left side connection point with the left side support body, and

right side connection members include a first right side connectionmember for connecting the first right side connection point with theright side support body and a second right side connection member forconnecting the second right side connection point with the right sidesupport body.

(7) According to a seventh aspect of the present invention, in thetorque sensor due to the aforementioned sixth aspect,

where two straight lines which pass through an intersection with therotation axis and are orthogonal to each other are drawn on the basicplane, orthogonal projection images of the first left side connectionpoint and the second left side connection point are disposed on a firststraight line and orthogonal projection images of the first right sideconnection point and the second right side connection point are disposedon a second straight line.

(8) According to an eighth aspect of the present invention, in thetorque sensor due to the aforementioned sixth aspect,

in order to detect torque around the Z axis in an XYZ three-dimensionalcoordinate system, the annular deformation body is disposed on the XYplane which is a basic plane, with the origin O given as the center, theleft side support body is disposed at a negative domain of the Z axis,and the right side support body is disposed at a positive domain of theZ axis,

the first left side connection point and the second left side connectionpoint are provided on a side surface of the annular deformation body onthe negative side of the Z axis, the first right side connection pointand the second right side connection point are provided on a sidesurface of the annular deformation body on the positive side of the Zaxis,

where both of the side surfaces of the annular deformation body areprojected on the XY plane to obtain orthogonal projection images, aprojection image of the first right side connection point is disposed onthe positive X axis, a projection image of the second right sideconnection point is disposed on the negative X axis, a projection imageof the first left side connection point is disposed on the positive Yaxis, and a projection image of the second left side connection point isdisposed on the negative Y axis, and

where the V axis is defined as a coordinate axis in which the X axis isrotated counterclockwise by 45 degrees on the XY plane, with the originO given as the center, and where the W axis is defined as a coordinateaxis in which the Y axis is rotated counterclockwise by 45 degrees, withthe origin O given as the center, the first detection point is disposedon the positive V axis, the second detection point is disposed on thepositive W axis, the third detection point is disposed on the negative Vaxis, and the fourth detection point is disposed on the negative W axis.

(9) According to a ninth aspect of the present invention, in the torquesensor due to the aforementioned fourth aspect,

n is set to be equal to 8, by which the annular deformation body isconstituted by disposing individual parts in the order of a firstcoupling part, a first detection part, a second coupling part, a seconddetection part, a third coupling part, a third detection part, a fourthcoupling part, a fourth detection part, a fifth coupling part, a fifthdetection part, a sixth coupling part, a sixth detection part, a seventhcoupling part, a seventh detection part, an eighth coupling part and aneighth detection part along the basic annular channel, a first left sideconnection point is disposed at the first coupling part, a first rightside connection point is disposed at the second coupling part, a secondleft side connection point is disposed at the third coupling part, asecond right side connection point is disposed at the fourth couplingpart, a third left side connection point is disposed at the fifthcoupling part, a third right side connection point is disposed at thesixth coupling part, a fourth left side connection point is disposed atthe seventh coupling part, and a fourth right side connection point isdisposed at the eighth coupling part,

left side connection members include a first left side connection memberwhich connects the first left side connection point with the left sidesupport body, a second left side connection member which connects thesecond left side connection point with the left side support body, athird left side connection member which connects the third left sideconnection point with the left side support body and a fourth left sideconnection member which connects the fourth left side connection pointwith the left side support body, and

right side connection members include a first right side connectionmember which connects the first right side connection point with theright side support body, a second right side connection member whichconnects the second right side connection point with the right sidesupport body, a third right side connection member which connects thethird right side connection point with the right side support body and afourth right side connection member which connects the fourth right sideconnection point with the right side support body.

(10) According to a tenth aspect of the present invention, in the torquesensor due to the aforementioned ninth aspect,

where four straight lines which pass through an intersection with therotation axis and intersect with each other by every 45-degree angledifference are drawn on the basic plane, orthogonal projection images ofthe first left side connection point and the third left side connectionpoint are disposed on a first straight line, orthogonal projectionimages of the first right side connection point and the third right sideconnection point are disposed on a second straight line, orthogonalprojection images of the second left side connection point and thefourth left side connection point are disposed on a third straight line,and orthogonal projection images of the second right side connectionpoint and the fourth right side connection point are disposed on afourth straight line.

(11) According to an eleventh aspect of the present invention, in thetorque sensor due to the aforementioned ninth aspect,

in order to detect torque around the Z axis in the XYZ three-dimensionalcoordinate system, the annular deformation body is disposed on the XYplane which is a basic plane, with the origin O given as the center, theleft side support body is disposed at a negative domain of the Z axis,and the right side support body is disposed at a positive domain of theZ axis,

the first to the fourth left side connection points are provided on aside surface of the annular deformation body on the negative side of theZ axis, and the first to the fourth right side connection points areprovided on a side surface of the annular deformation body on thepositive side of the Z axis,

where the V axis is defined as a coordinate axis in which the X axis isrotated counterclockwise by 45 degrees on the XY plane, with the originO given as the center, the W axis is defined as a coordinate axis inwhich the Y axis is rotated counterclockwise by 45 degrees, with theorigin O given as the center, and where both side surfaces of theannular deformation body are projected on the XY plane to obtainorthogonal projection images, a projection image of the first left sideconnection point is disposed on the positive X axis, a projection imageof the second left side connection point is disposed on the positive Yaxis, a projection image of the third left side connection point isdisposed on the negative X axis, a projection image of the fourth leftside connection point is disposed on the negative Y axis, a projectionimage of the first right side connection point is disposed on thepositive V axis, a projection image of the second right side connectionpoint is disposed on the positive W axis, a projection image of thethird right side connection point is disposed on the negative V axis,and a projection image of the fourth right side connection point isdisposed on the negative W axis, and

when a directional vector V_(ec) (θ) which gives an angle θcounterclockwise in the positive direction of the X axis is defined onthe XY plane, with the origin O given as a starting point, an i-thdetection point (1≤i≤8) is disposed at a position at which thedirectional vector V_(ec) (π/8+(I−1)·π/4) intersects with the basicannular channel.

(12) According to a twelfth aspect of the present invention, in thetorque sensor due to the aforementioned second to eleventh aspects,

of n number of the plurality of detection parts, some of them are firstattribute detection parts, and the others are second attribute detectionparts,

a first attribute displacement part which constitutes the firstattribute detection part undergoes displacement in a direction movingaway from the right side support body, upon exertion of torque in afirst rotating direction and undergoes displacement in a directionmoving close to the right side support body upon exertion of torque in asecond rotating direction which is reverse to the first rotatingdirection,

a second attribute displacement part which constitutes the secondattribute detection part undergoes displacement in a direction movingclose to the right side support body upon exertion of torque in thefirst rotating direction and undergoes displacement in a directionmoving away from the right side support body upon exertion of torque inthe second rotating direction,

a first attribute capacitive element is constituted of a first attributedisplacement electrode which is fixed to the first attributedisplacement part and a first attribute fixed electrode which is fixedat a position of the right side support body which opposes the firstattribute displacement electrode,

a second attribute capacitive element is constituted of a secondattribute displacement electrode which is fixed at the second attributedisplacement part and a second attribute fixed electrode which is fixedat a position of the right side support body which opposes the secondattribute displacement electrode, and

the detection circuits output an electric signal corresponding to adifference between a capacitance value of the first attribute capacitiveelement and a capacitance value of the second attribute capacitiveelement as an electric signal which indicates exerted torque.

(13) According to a thirteenth aspect of the present invention, in thetorque sensor due to the aforementioned first to twelfth aspects,

the detection part which has a first deformation part, a seconddeformation part and a displacement part is disposed between onecoupling part end portion and the other coupling part end portion,

the first deformation part is constituted of a first plate-shaped piecehaving flexibility, the second deformation part is constituted of asecond plate-shaped piece having flexibility, and the displacement partis constituted of a third plate-shaped piece,

an external end of the first plate-shaped piece is connected to the onecoupling part end portion, while an internal end of the firstplate-shaped piece is connected to one end of the third plate-shapedpiece, and an external end of the second plate-shaped piece is connectedto the other coupling part end portion, while an internal end of thesecond plate-shaped piece is connected to the other end of the thirdplate-shaped piece.

(14) According to a fourteenth aspect of the present invention, in thetorque sensor due to the aforementioned thirteenth aspect,

in a state that no torque is exerted, the third plate-shaped piece andthe opposing surface of the right side support body are kept parallel toeach other.

(15) According to a fifteenth aspect of the present invention, in thetorque sensor due to the aforementioned fourteenth aspect,

when a normal line orthogonal to the basic plane is provided at aposition of the detection point, the first plate-shaped piece and thesecond plate-shaped piece which constitute the detection part positionedat the detection point are inclined to the normal line, and also thefirst plate-shaped piece is inclined so as to be reverse in direction tothe second plate-shaped piece.

(16) According to a sixteenth aspect of the present invention, in thetorque sensor due to the aforementioned first to fifteenth aspects,

when a connection reference line parallel to the rotation axis passesthrough the left side connection points is defined, auxiliary connectionmembers disposed on the connection reference line or the vicinitythereof are additionally provided between the right side surfaces of thecoupling parts of the annular deformation body and the opposing surfaceof the right side support body.

(17) According to a seventeenth aspect of the present invention, in thetorque sensor due to the aforementioned sixteenth aspect,

as the auxiliary connection members, there is used a member which ismore likely to undergo elastic deformation when force is exerted in adirection orthogonal to the connection reference line in comparison witha case where force is exerted in a direction along the connectionreference line.

(18) According to an eighteenth aspect of the present invention, in thetorque sensor due to the aforementioned sixteenth or seventeenth aspect,

a connecting part of an annular deformation body with an auxiliaryconnection member or a connecting part of a right side support body withan auxiliary connection member or both of the connecting parts areconstituted of diaphragm parts, and the auxiliary connection member isinclined to the connection reference line by deformation of thediaphragm parts on the basis of exertion of torque.

(19) According to a nineteenth aspect of the present invention, in thetorque sensor due to the aforementioned eighteenth aspect,

the connecting part of the annular deformation body with the auxiliaryconnection member is constituted of the diaphragm part, and

left side connection members are kept away from the diaphragm part ofthe annular deformation body and connected to a circumferential partthereof.

(20) According to a twentieth aspect of the present invention, in thetorque sensor due to the aforementioned first to nineteenth aspects,

annular structural bodies which have through-opening parts at the centerare used as the left side support body and the right side support body,and there is secured an insertion hole which penetrates through therespective through-opening parts of the left side support body, theannular deformation body (50) and the right side support body along therotation axis.

(21) According to a twenty-first aspect of the present invention, in thetorque sensor due to the aforementioned first to twentieth aspects,

the annular deformation body is a member which is obtained by givingpartial material-removal processing to a circular annular memberobtained by forming a through-opening part in the shape of a concentricdisk smaller in diameter at the center of a disk disposed, with therotation axis given as the central axis, and the detection part isconstituted of a part to which the material-removal processing is given.

(22) According to a twenty-second aspect of the present invention, inthe torque sensor due to the aforementioned first to twenty-firstaspects,

the left side support body and the right side support body are composedof circular annular members which are obtained by formingthrough-opening parts in the shape of a concentric disk smaller indiameter at the center of a disk disposed, with the rotation axis givenas the central axis.

(23) According to a twenty-third aspect of the present invention, in thetorque sensor due to the aforementioned first to twenty-second aspects,

the left side connection members are each constituted of a protrudingpart which protrudes from the right side surface of the left sidesupport body to rightward, the right side connection members are eachconstituted of a protruding part which protrudes from the left sidesurface of the right side support body to leftward, and a top surface ofeach of the protruding parts is joined to a position of each of theconnection points of the annular deformation body.

(24) According to a twenty-fourth aspect of the present invention, inthe torque sensor due to the aforementioned first to twenty-thirdaspects,

even where a relative position of the displacement electrode to thefixed electrode is changed as a result of exertion of torque in apredetermined rotating direction, one of the fixed electrode and of thedisplacement electrode is set to be larger in area than the other sothat the pair of electrodes constituting the capacitive element are notchanged in effective opposing area.

(25) According to a twenty-fifth aspect of the present invention, in thetorque sensor due to the aforementioned first to twenty-fourth aspects,

the left side support body, the right side support body and the annulardeformation body are each constituted of a conductive material, thedisplacement electrode is formed on the surface of the displacement partvia an insulating layer, and the fixed electrode is formed on thesurface of the right side support body via an insulating layer.

(26) According to a twenty-sixth aspect of the present invention, in thetorque sensor due to the aforementioned first to twenty-fourth aspects,

the left side support body, the right side support body and the annulardeformation body are each constituted of a conductive material, thedisplacement electrode s constituted of a certain domain of the surfaceof the annular deformation body or the fixed electrode is constituted ofa certain domain of the surface of the right side support body.

(27) According to a twenty-seventh aspect of the present invention, in atorque sensor which detects torque around a predetermined rotation axis,

the torque sensor comprising:

an annular deformation body which extends along a basic annular channelwhen the basic annular channel is defined so as to surround acircumference of the rotation axis on a basic plane which is orthogonalto the rotation axis;

an exertion support body which is disposed at a position adjacent to theleft side of the annular deformation body when viewed from a referenceobservation direction in which the rotation axis gives a horizontal lineextending laterally;

a fixing support body which is disposed at a position adjacent to theright side of the annular deformation body when viewed from thereference observation direction;

exertion connection members which connect exertion connection pointsprovided at a predetermined site of the annular deformation body withthe exertion support body;

fixing connection members which connect fixing connection pointsprovided at a predetermined site of the annular deformation body withthe fixing support body;

a capacitive element which is constituted of a displacement electrodefixed at a predetermined position of the right side surface of theannular deformation body and a fixed electrode fixed at a position ofthe fixing support body which opposes the displacement electrode; and

detection circuits which output electric signals indicating torquearound the rotation axis exerted on one of the exertion support body andof the fixing support body in a state that a load is applied to theother on the basis of fluctuation in capacitance value of the capacitiveelement; wherein

the annular deformation body is provided with a detection partpositioned at a detection point defined on the basic annular channel anda coupling part connected to both ends of the detection part,

the detection part is provided with a first deformation part whichundergoes elastic deformation by exertion of torque which is to bedetected, a second deformation part which undergoes elastic deformationby exertion of torque which is to be detected and a displacement partwhich undergoes displacement resulting from elastic deformation of thefirst deformation part and the second deformation part,

an external end of the first deformation part is connected to a couplingpart adjacent thereto, while an internal end of the first deformationpart is connected to the displacement part, and an external end of thesecond deformation part is connected to a coupling part adjacentthereto, while an internal end of the second deformation part isconnected to the displacement part,

the displacement electrode is fixed at a position of the displacementpart which opposes the fixing support body, and

the exertion connection points and the fixing connection points aredisposed at the coupling part, orthogonal projection images of theexertion connection points on the basic plane and orthogonal projectionimages of the fixing connection points on the basic plane are formed atmutually different positions.

(28) According to a twenty-eighth aspect of the present invention, in atorque sensor which detects torque around a predetermined rotation axis,

the torque sensor comprising:

an annular deformation body which extends along a basic annular channelwhen the basic annular channel is defined so as to surround acircumference of the rotation axis on a basic plane which is orthogonalto the rotation axis;

an exertion support body which is disposed at a position adjacent to theoutside or the inside of the annular deformation body;

a fixing support body which is disposed at a position adjacent to theright side of the annular deformation body when viewed from a referenceobservation direction in which the rotation axis gives a horizontal lineextending laterally;

exertion connection members which connect exertion connection pointsprovided at a predetermined site of the annular deformation body withthe exertion support body;

fixing connection members which connect fixing connection pointsprovided at a predetermined site of the annular deformation body withthe fixing support body;

a capacitive element which is constituted of a displacement electrodefixed at a predetermined position of the right side surface of theannular deformation body and a fixed electrode fixed at a position ofthe fixing support body which opposes the displacement electrode; and

detection circuits which output electric signals indicating torquearound the rotation axis exerted on one of the exertion support body andof the fixing support body in a state that a load is applied to theother on the basis of fluctuation in capacitance value of the capacitiveelement; wherein

the annular deformation body is provided with a detection part which ispositioned at a detection point defined on the basic annular channel anda coupling part which is connected to both ends of the detection part,

the detection part is provided with a first deformation part whichundergoes elastic deformation by exertion of torque which is to bedetected, a second deformation part which undergoes elastic deformationby exertion of torque which is to be detected and a displacement partwhich undergoes displacement resulting from elastic deformation of thefirst deformation part and the second deformation part,

an external end of the first deformation part is connected to a couplingpart adjacent thereto, while an internal end of the first deformationpart is connected to the displacement part, and an external end of thesecond deformation part is connected to a coupling part adjacentthereto, while an internal end of the second deformation part isconnected to the displacement part,

the displacement electrode is fixed at a position of the displacementpart which opposes the fixing support body, and

the exertion connection points and the fixing connection points aredisposed at the coupling part, orthogonal projection images of theexertion connection points on the basic plane and orthogonal projectionimages of the fixing connection points on the basic plane are formed atmutually different positions.

(29) According to a twenty-ninth aspect of the present invention, in atorque sensor which detects torque around a predetermined rotation axis,

the torque sensor comprising:

an annular deformation body which extends along a basic annular channelwhen the basic annular channel is defined so as to surround acircumference of the rotation axis on a basic plane which is orthogonalto the rotation axis;

an exertion support body which exerts torque on the annular deformationbody;

a fixing support body which fixes the annular deformation body;

exertion connection members which connect exertion connection pointsprovided at a predetermined site of the annular deformation body withthe exertion support body;

fixing connection members which connect fixing connection pointsprovided at a predetermined site of the annular deformation body withthe fixing support body;

a detection element which detects elastic deformation occurring at theannular deformation body; and

detection circuits which detect electric signals indicating torquearound the rotation axis exerted on one of the exertion support body andof the fixing support body in a state that a load is applied to theother on the basis of detection results of the detection element;wherein

the annular deformation body is provided with a detection partpositioned at a detection point defined on the basic annular channel anda coupling part connected to both ends of the detection part,

the exertion connection points and the fixing connection points aredisposed at the coupling part, and orthogonal projection images of theexertion connection points on the basic plane and orthogonal projectionimages of the fixing connection points on the basic plane are formed atmutually different positions, and

the detection part is provided with an elastic deformation structurepart which undergoes elastic deformation, upon exertion of force betweenthe exertion connection point and the fixing connection point, on thebasis of the thus exerted force, and the detection element detectselastic deformation occurring at the elastic deformation structure part.

(30) According to a thirtieth aspect of the present invention, in thetorque sensor due to the aforementioned twenty-ninth aspect,

the detection part is provided with a first deformation part whichundergoes elastic deformation by exertion of torque to be detected, asecond deformation part which undergoes elastic deformation by exertionof torque to be detected and a displacement part which undergoesdisplacement resulting from elastic deformation of the first deformationpart and the second deformation part, and

an external end of the first deformation part is connected to a couplingpart adjacent thereto, while an internal end of the first deformationpart is connected to the displacement part, and an external end of thesecond deformation part is connected to a coupling part adjacentthereto, while an internal end of the second deformation part isconnected to the displacement part.

(31) According to a thirty-first aspect of the present invention, in thetorque sensor due to the aforementioned twenty-ninth or thirtiethaspect,

the detection element is constituted of the capacitive element which hasa displacement electrode fixed at a predetermined position of thedetection part and a fixed electrode fixed at a position of the exertionsupport body or the fixing support body which opposes the displacementelectrode,

the displacement electrode is disposed at a position which causesdisplacement to the fixed electrode on the basis of elastic deformationoccurring at the detection part, and

the detection circuits output electric signals indicating exerted torqueon the basis of fluctuation in capacitance value of the capacitiveelement.

(32) According to a thirty-second aspect of the present invention, inthe torque sensor due to the aforementioned twenty-ninth aspect,

the detection part is provided with a plate-shaped deformation partwhich undergoes elastic deformation by exertion of torque to bedetected, and the plate-shaped deformation part is disposed so that aplate surface thereof is inclined to the basic annular channel.

(33) According to a thirty-third aspect of the present invention, in thetorque sensor due to the aforementioned thirty-second aspect,

the detection element is constituted of strain gauges (r1 to r4) fixedat a position of the detection part which causes elastic deformation,and

the detection circuit outputs an electric signal indicating exertedtorque on the basis of fluctuation in electrical resistance of thestrain gauges.

(34) According to a thirty-fourth aspect of the present invention, inthe torque sensor due to the aforementioned thirty-third aspect,

the detection element is constituted of strain gauges which are disposedon both surfaces of the plate-shaped deformation part in the vicinity ofan end thereof which is connected with a coupling part.

(35) According to a thirty-fifth aspect of the present invention, in thetorque sensor due to the aforementioned thirty-fourth aspect,

the detection element is provided with a first strain gauge and a secondstrain gauge which are disposed respectively on a front surface and arear surface in the vicinity of a first connection end with a couplingpart and a third strain gauge and a fourth strain gauge which aredisposed respectively on a front surface and a rear surface in thevicinity of a second connection end with a coupling part, and

the detection circuit detects a bridge voltage of a bridge circuit inwhich the first strain gauge and the fourth strain gauge are given as afirst opposite side, while the second strain gauge and the third straingauge are given as a second opposite side.

Effects of the Invention

In the torque sensor according to the present invention, torquedetection is performed by using an annular deformation body having athrough-opening part through which a rotation axis is inserted. A leftside support body and a right side support body are disposed on bothleft and right sides of the annular deformation body, and these areindividually joined to different connection points. Therefore, whentorque is applied to one of the support bodies, with a load applied tothe other of the support bodies, distortion occurs in the annulardeformation body. A detection part is provided at a predetermined siteof the annular deformation body, and the detection part is provided witha pair of deformation parts which cause elastic deformation by exertionof torque to be detected and a displacement part which causesdisplacement resulting from elastic deformation of the pair ofdeformation parts. Upon exertion of torque, displacement occurs at thedisplacement part, resulting in change in distance in relation to theright side support body. In the present invention, the change indistance can be detected by referring to a capacitance value of acapacitive element. That is, it is possible to recognize a mode ofdeformation of the annular deformation body and detect torque which isexerted on the basis of an amount of fluctuation in capacitance value ofthe capacitive element which is constituted of a displacement electrodefixed at a displacement part and a fixed electrode fixed at the rightside support body which is disposed at a position opposing thedisplacement electrode.

The annular deformation body, the left side support body and the rightside support body can be each constituted of a flat structural bodywhich is small in thickness in an axis direction and, therefore, anentire axial length of the sensor can be set shorter. Further, sincetorque is detected on the basis of distortion at a detection part of theannular deformation body, the detection part is required to be made of amaterial which will cause elastic deformation and even where a materialrelatively high in rigidity is used as the annular deformation body,detection can be made at high accuracy. Further, distortion of the shapeof the annular deformation body can be detected by a capacitive elementwhich is constituted of a displacement electrode fixed at thedisplacement part and a fixed electrode fixed to the right side supportbody which opposes thereto. Therefore, the sensor is made simple instructure and the fixed electrode can be easily adjusted for a positionthereof. It is, thus, possible to provide the torque sensor which issmall in size, high in rigidity and capable of realizing high productionefficiency.

In particular, two upper and lower sites of the annular deformation bodyare joined to the left side support body, and two left and right sitesthereof are joined to the right side support body so that eachconnection point deviates by every 90 degrees, thus making it possibleto deform the annular deformation body efficiently by exertion oftorque. It is also true for a case where each of the connection pointsis allowed to deviate by every 45 degrees so that four sites are joinedto the left side support body and four sites are also joined to theright side support body.

Further, upon exertion of the same torque, a capacitive element with anincreasing electrode interval and a capacitive element with a decreasingelectrode interval are used to detect torque which is exerted as adifference between both capacitance values, thus making it possible toperform stable torque detection in which common-mode noise andzero-point drift are suppressed. This detection can contribute tosetting off influences of expansion of individual parts due totemperatures to obtain a highly accurate detection value. It is alsopossible to obtain an accurate detection value from which interferencewith the other axis components are removed.

In the torque sensor according to the present invention, it is possibleto form a through-opening part through which a rotation axis is insertednot only on the annular deformation body but also on the left sidesupport body and the right side support body. Thereby, it is possible tosecure an insertion hole which penetrates through the through-openingpart of each of the left side support body, the annular deformation bodyand the right side support body along the rotation axis, providing astructure, the interior of which is hollow. As a result, where thetorque sensor according to the present invention is used integrated intoa joint part of a robot arm, a decelerator, etc., can be disposed at thehollow part, thus making it possible to design a generally space-savingrobot arm.

Further, an auxiliary connection member is provided between a right sidesurface of a coupling part of the annular deformation body and anopposing surface of the right side support body, by which it is possibleto suppress influences of interference components other than torque tobe detected (rotational moment) around a predetermined rotation axis.Therefore, it is possible to reduce an error resulting from interferencewith the other axis components and perform more accurate detection.

It is noted that in place of the left side support body and the rightside support body, an exertion support body and a fixing support bodyare used, and the fixing support body is disposed on the right-hand sideof the annular deformation body, as with the right side support body,and the exertion support body is disposed outside or inside the annulardeformation body, by which substantially similar effects can beobtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a basic structural part of thetorque sensor of the prior application.

FIG. 2 is a side view of the basic structural part of the torque sensorof the prior application obtained by joining three constituents shown inFIG. 1 to each other.

FIG. 3 is a side sectional view in which the basic structural part shownin FIG. 2 is cut along a YZ plane.

FIG. 4 is a front view of a left side support body 10 and protrudingparts 11, 12 shown in FIG. 1, when viewed from the right side in FIG. 1.

FIG. 5 is a front view of an annular deformation body 30 shown in FIG. 1when viewed from the right side in FIG. 1.

FIG. 6 is a front view of a right side support body 20 and protrudingparts 21, 22 shown in FIG. 1, when viewed from the right side in FIG. 1.

FIG. 7 is a sectional view in which the basic structural part shown inFIG. 2 is cut along an XY plane, when viewed from the left side in FIG.2.

FIG. 8 is a sectional view on the XY plane which shows a deformationstate when torque which is positive rotation around the Z axis isexerted on the basic structural part shown in FIG. 2 (this is asectional view in which the basic structural part shown in FIG. 2 is cutalong the XY plane, when viewed from the left side in FIG. 2. The brokenline indicates a state before deformation).

FIG. 9 is a plan view which shows the annular deformation body 30 in astate that displacement electrodes E31, E32 are formed on an innercircumferential surface thereof, when viewed from the left side in FIG.2.

FIG. 10 is a plan view which shows the right side support body 20 in astate that fixed electrodes E21, E22 are attached, when viewed from theleft side in FIG. 2.

FIG. 11 is a side view which shows the right side support body 20 shownin FIG. 10.

FIG. 12 is a side sectional view in which a structural body obtained byadding a displacement electrode and a fixed electrode to the basicstructural part shown in FIG. 3 is cut along a VZ plane (the upside ofFIG. 12 is the direction of the V axis shown in FIG. 9 and FIG. 10).

FIG. 13 is a sectional view in which a structural body obtained byadding the displacement electrode and the fixed electrode to the basicstructural part shown in FIG. 2 is cut along the XY plane, when viewedfrom the left side in FIG. 2.

FIG. 14 is a sectional view which shows a state when torque which ispositive rotation around the Z axis is exerted on the basic structuralpart shown in FIG. 13 (the broken line indicates a state beforedeformation).

FIG. 15 is an exploded perspective view which shows a basic structuralpart of a torque sensor according to a basic embodiment of the presentinvention.

FIG. 16 is a side view which shows the basic structural part of thetorque sensor according to the basic embodiment of the present inventionwhich is obtained by joining three constituents shown in FIG. 15 to eachother.

FIG. 17 is a front view of an annular deformation body 50 shown in FIG.15, when viewed from the right side in FIG. 15.

FIG. 18 is a projection view on the XY plane which indicates adisposition of individual detection points and individual connectionpoints on the annular deformation body 50 shown in FIG. 15 (this is aview from the side of the right side support body 20: the annulardeformation body 50 is shown only by a contour thereof).

FIG. 19 covers partial sectional views, each of which shows a detailedstructure of detection parts D1 to D4 of the annular deformation body 50shown in FIG. 15 (representatively indicated by the symbol D).

FIG. 20 is a partial sectional view which shows a detailed structure inwhich an electrode is provided at the detection parts D1 to D4(representatively indicated by the symbol D) on the annular deformationbody 50 shown in FIG. 15 and at predetermined parts of the right sidesupport body 20 which oppose thereto.

FIG. 21 is a sectional view on the XY plane which shows a deformationstate when torque +Mz which is positive rotation around the Z axis isexerted on the left side support body 10 of the basic structural partshown in FIG. 15 (a sectional view in which the basic structural partshown in FIG. 15 is cut along the XY plane and viewed from the rightside in FIG. 15. The broken line indicates a state before deformation).

FIG. 22 is a table which shows behavior of each of the detection partsupon occurrence of the deformation shown in FIG. 21.

FIG. 23 is a circuit diagram which shows one example of a detectioncircuit used in the torque sensor according to the basic embodimentshown in FIG. 15.

FIG. 24A and FIG. 24B are drawings which show the principle of keepingconstant the effective area of a capacitive element even upon change inrelative position of a displacement electrode in relation to a fixedelectrode.

FIG. 25 is a table which shows an actual example of a specificdisplacement amount of an electrode distance of each of capacitiveelements when force in the direction of each axis or moment around eachaxis is exerted on the left side support body 10 at the basic structuralpart shown in FIG. 16.

FIG. 26 is a table prepared on the basis of the table shown in FIG. 25which shows an amount of fluctuation (an extent of increase or decrease)in capacitance value of each of capacitive elements.

FIG. 27 is a sectional view on the XY plane which shows a deformationstate when +Fx in the positive direction of the X axis is exerted on theleft side support body 10 at the basic structural part shown in FIG. 15(a sectional view in which the basic structural part shown in FIG. 15 iscut along the XY plane, when viewed from the right side in FIG. 15. Thebroken line indicates a state before deformation).

FIG. 28 is a side view which shows a deformation state when moment +Mxwhich is positive rotation around the X axis is exerted on the left sidesupport body 10 at the basic structural part shown in FIG. 15.

FIG. 29 is an exploded perspective view which shows a basic structuralpart of a torque sensor according to a modification example of thepresent invention to which an auxiliary connection member is added.

FIG. 30 is a side view of a basic structural part of the torque sensorwhich is obtained by joining the three constituents shown in FIG. 29 toeach other.

FIG. 31 is a front view which shows a state in which auxiliaryconnection members 23, 24 are joined to the annular deformation body 50shown in FIG. 29, when viewed from the right side in FIG. 29.

FIG. 32 is a partial sectional view which shows a structure in thevicinity of the auxiliary connection member 23 at the basic structuralpart shown in FIG. 29.

FIG. 33 is a partial sectional view which shows a modification exampleof the structure in the vicinity of the auxiliary connection membershown in FIG. 32.

FIG. 34 is a table which shows an amount of fluctuation (an extent ofincrease or decrease) in capacitance value of each of capacitiveelements when force in the direction of each axis or moment around eachaxis is exerted on the left side support body 10 in the modificationexample to which the auxiliary connection member shown in FIG. 29 isadded.

FIG. 35 is a front view (a drawing when viewed from the side of theright side support body 20) of an annular deformation body 60 of atorque sensor according to a modification example of the presentinvention in which eight sets of detection parts are used.

FIG. 36 is a plan view which shows a disposition of detection parts andcoupling parts of the annular deformation body 60 shown in FIG. 35(hatching is given for indicating a domain of each detection part andnot for indicating a cross section).

FIG. 37 is a projection view on the XY plane which indicates adisposition of individual detection points and individual connectionpoints of the annular deformation body 60 shown in FIG. 35 (a drawingwhen viewed from the side of the right side support body 20: the annulardeformation body 60 is indicated only by a contour thereof).

FIG. 38 is a table which shows an amount of fluctuation (an extent ofincrease or decrease) in capacitance value of each of capacitiveelements when force in the direction of each axis or moment around eachaxis is exerted on the left side support body 10 of the modificationexample which uses eight sets of the detection parts shown in FIG. 35.

FIG. 39 is a drawing which shows variations of a formula for calculatingmoment Mz around the Z axis (torque to be detected) in the modificationexample which uses the eight sets of detection parts shown in FIG. 35.

FIG. 40 is a table which shows an amount of fluctuation (an extent ofincrease or decrease) in capacitance value of each of capacitiveelements when force in the direction of each axis or moment around eachaxis is exerted on the left side support body 10 in a torque sensor inwhich an auxiliary connection member is additionally added to themodification example which uses the eight sets of detection parts shownin FIG. 35.

FIG. 41 is a partial sectional view which shows variations of astructure of the detection part in the present invention.

FIG. 42 is a front view of a square-shaped annular deformation body 60Swhich can be used in the present invention (a drawing when viewed fromthe side of the right side support body 20).

FIG. 43 is a plan view which shows a disposition of detection parts andcoupling parts of the square-shaped annular deformation body 60S shownin FIG. 42 (hatching is given for indicating a domain of each detectionpart and not for indicating a cross section).

FIG. 44 is a projection view on the XY plane which shows a dispositionof individual detection points and individual connection points of thesquare-shaped annular deformation body 60S shown in FIG. 43 (a drawingwhen viewed from the side of the right side support body 20: the annulardeformation body 60S is indicated only by a contour thereof).

FIG. 45 is a side view of a basic structural part of a modificationexample which supports the annular deformation body 50 by an exertionsupport body 70 from the outside (the part of the exertion support body70 indicates the cross section).

FIG. 46 is a front view of the annular deformation body 50 and theexertion support body 70 shown in FIG. 45, when viewed from the rightside in FIG. 45.

FIG. 47 is a side sectional view in which the basic structural part ofthe modification example which supports the annular deformation body 50from the inside by an exertion support body 80 is cut along the YZplane.

FIG. 48 is a front view of the annular deformation body 50 and theexertion support body 80 shown in FIG. 47, when viewed from the rightside in FIG. 47.

FIG. 49 is a front view which shows a state that the annular deformationbody 60 shown in FIG. 35 is supported from the outside by the exertionsupport body 70, when viewed from the right side.

FIG. 50 is a front view which shows a state that the annular deformationbody 60 shown in FIG. 35 is supported from the inside by the exertionsupport body 80, when viewed from the right side.

FIG. 51 covers a plan view (a view at the upper part) which shows anannular deformation body 90 having detection parts D1′ to D4′ disposedso that a displacement part 93 faces outside and the exertion supportbody 70 disposed outside thereof, and a side sectional view (a view atthe lower part) in which a basic structural part constituted by adding afixing support body 120 thereto is cut along the XZ plane.

FIG. 52 covers partial sectional views, each of which shows a mode ofelastic deformation of a plate-shaped deformation part 41 whichconstitutes a detection part DD simpler in structure.

FIG. 53A covers a side view and FIG. 53B covers a plan view, each ofwhich shows an example in which a strain gauge is used as a detectionelement for detecting elastic deformation occurring at the detectionpart DD shown in FIG. 52(a).

FIG. 54 is a circuit diagram which shows a bridge circuit for outputtingan electric signal on the basis of detection results of four sets ofstrain gauges shown in FIG. 53.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a description will be given of the present invention on thebasis of the embodiment shown in the drawings. The present invention isan invention obtained by improving the torque sensor of the priorapplication which is disclosed in Patent Document 9 described above (WO2012/018031). For the sake of convenience of description, at first, inthe following Sections 1 to 3, a description will be given of the torquesensor of the prior application. In Section 4 and subsequent Sections, adescription will be given of characteristics of the present invention.

<<<Section 1. Characteristics of the Basic Structural Part in TorqueSensor of the Prior Application>>>

FIG. 1 is an exploded perspective view which shows a basic structuralpart of the torque sensor of the prior application. As shown in thedrawing, the basic structural part is constituted by disposing anannular deformation body 30 between a left side support body 10 and aright side support body 20 and joining these three constituents to eachother. Here, for the sake of convenience, as shown in the drawing, anXYZ three-dimensional coordinate system is defined to give the followingdescription. Here, the Z axis drawn horizontally in the drawingcorresponds to a rotation axis of torque to be detected, and the torquesensor has functions to detect torque around the rotation axis (aroundthe Z axis).

The annular deformation body 30 disposed at the center of the drawing ismade of a material which causes elastic deformation by exertion oftorque to be detected, and there is formed in the interior thereof athrough-opening part H30 through which the rotation axis (Z axis) isinserted. On the other hand, the left side support body 10 disposed onthe left side in the drawing is a member which supports the left sidesurface of the annular deformation body 30. The right side support body20 disposed on the right-hand side in the drawing is a member whichsupports the right side surface of the annular deformation body 30. Inthe torque sensor of the prior application shown in the drawing, theleft side support body 10 is an annular member having a through-openingpart H10 through which the rotation axis (Z axis) is inserted, and theright side support body 20 is an annular member having a through-openingpart H20 through which the rotation axis (Z axis) is inserted.

In general, the concepts of the right side and the left side conceptsthat only carry meaning when an observation is made in a specificobservation direction. Here, for the sake of convenience of description,as shown in FIG. 1, when an observation is made in a referenceobservation direction in which the rotation axis (Z axis) gives ahorizontal line extending laterally (an observation direction in whichthe rightward direction is the positive direction of the Z axis), asupport body which is disposed at a position adjacent to the left sideof the annular deformation body 30 is referred to as the left sidesupport body 10, whereas a support body which is disposed at a positionadjacent to the right side of the annular deformation body 30 isreferred to as the right side support body 20.

Here, the origin O of the XYZ three-dimensional coordinate system isdefined at the center of the annular deformation body 30, and the leftside support body 10, the annular deformation body 30 and the right sidesupport body 20 are each constituted of a circular annular member inwhich the Z axis is given as a central axis. More specifically, theannular deformation body 30 is composed of a circular annular memberwhich is obtained by forming the through-opening part H30 in the shapeof a concentric disk smaller in diameter at the center of a diskdisposed, with the Z axis (rotation axis) given as the central axis.Similarly, the left side support body 10 and the right side support body20 are also each composed of a circular annular member which is obtainedby forming respectively the through-opening parts H10, H20 in the shapeof a concentric disk smaller in diameter at the center of a diskdisposed, with the Z axis (rotation axis) given as the central axis.

On the other hand, two fan-shaped protruding parts 11, 12 which protrudeto the right are provided on the right side surface of the left sidesupport body 10, and top surfaces of the protruding parts 11, 12 arejoined to the left side surface of the annular deformation body 30. Asshown in the drawing,

the protruding part 11 is joined to an upper part (a part positioned inthe positive direction of the Y axis) of the annular deformation body30, and the protruding part 12 is joined to a lower part (a partpositioned in the negative direction of the Y axis) of the annulardeformation body 30. Similarly, two fan-shaped protruding parts 21, 22protruding to the left are provided on the left side surface of theright side support body 20. Top surfaces of the protruding parts 21, 22are joined to the right side surface of the annular deformation body 30.As shown in the drawing, the protruding part 21 is joined to a far part(a part positioned in the positive direction of the X axis) of theannular deformation body 30, and the protruding part 22 is joined to anear part (a part positioned in the negative direction of the X axis) ofthe annular deformation body 30.

FIG. 2 is a side view of a basic structural part of the torque sensorwhich is obtained by joining the three constituents shown in FIG. 1 toeach other. FIG. 3 is a side sectional view in which the basicstructural part is cut along the YZ plane. In the case of the exampleshown here, as shown in FIG. 3, the protruding parts 11, 12 are each astructural body which is formed integrally with the left side supportbody 10, and the top surfaces thereof are joined to the left sidesurface of the annular deformation body 30. Similarly, the protrudingparts 21, 22 are each a structural body which is formed integrally withthe right side support body 20, and the top surfaces thereof are joinedto the right side surface of the annular deformation body 30.

Consequently, the protruding parts 11, 12 function as the left-sideconnection members which connect left side connection points on the leftside surface of the annular deformation body 30 which opposes the leftside support body 10 with the left side support body 10. The protrudingparts 21, 22 function as the right-side connection members which connectright side connection points on the right side surface of the annulardeformation body 30 which opposes the right side support body 20 withthe right side support body 20.

FIG. 4 is a front view of the left side support body 10 and theprotruding parts 11, 12, when viewed from the right side in FIG. 1. FIG.5 is a front view of the annular deformation body 30, when viewed fromthe right side in FIG. 1. FIG. 6 is a front view of the right sidesupport body 20 and the protruding parts 21, 22, when viewed from theright side in FIG. 1. In FIG. 4, points P11, P12 which are indicated bya white dot at the center position of each of the protruding parts 11,12 are the left side connection points. These are used for describingconnection positions with the annular deformation body 30 in Section 2.Similarly, in FIG. 6, points P21, P22 which are indicated by the blackdot at the center position of each of the protruding parts 21, 22 arethe right side connection points. These are also used for describingconnection positions with the annular deformation body 30 in Section 2.

It is preferable that the components (the left side support body 10 andthe protruding parts 11, 12) shown in FIG. 4 are in actuality madecompletely identical to the components (the right side support body 20and the protruding parts 21, 22) shown in FIG. 6. In this case, thecomponents shown in FIG. 4 are rotated by 180 degrees, with the Y axisgiven as the rotation axis, and reversed, and these are then rotated by90 degrees, with the Z axis given as the rotation axis, by which theseare exactly in agreement with the components shown in FIG. 6. Therefore,in actuality, the basic structural part shown in FIG. 2 can beconstituted by preparing the two sets of components shown in FIG. 4 andone set of the components shown in FIG. 5.

As shown in FIG. 5, the circular through-opening part H30 is provided onthe annular deformation body 30. This is to cause elastic deformationwhich is necessary for detection. As will be described below, wheretorque to be detected is exerted on the basic structural part, theannular deformation body 30 is required to undergo deformation into anelliptical shape. Ease in such elastic deformation of the annulardeformation body 30 serves as a parameter that affects the detectionsensitivity of the sensor. Use of an annular deformation body 30 whichwill easily undergo elastic deformation makes it possible to produce asensor high in sensitivity capable of detecting even subtle torque.However, a maximum value of detectable torque is suppressed. Incontrast, use of an annular deformation body 30 which is less likely toundergo elastic deformation makes it possible to increase a maximumvalue of torque which can be detected. However, the sensitivity isdecreased to result in inability to detect subtle torque.

Ease in elastic deformation of the annular deformation body 30 dependson the thickness in the direction of the Z axis (the thinner, elasticdeformation will take more easily) and the diameter of thethrough-opening part H30 (the larger, elastic deformation will takeplace more easily). Further, the ease also depends on a materialthereof. Therefore, in practice, various parts of the annulardeformation body 30 may be appropriately selected for dimensions andmaterials depending on the application of the torque sensor.

On the other hand, in the principle of detecting torque, the left sidesupport body 10 or the right side support body 20 is not required to bea member which causes elastic deformation. Rather, it is preferable thatthe left side support body 10 and the right side support body 20 are aperfect rigid body in order that torque which has been exertedcontributes completely to deformation of the annular deformation body30. In the example shown in the drawing, as the left side support body10 and the right side support body 20, there are used the annularstructural bodies respectively having the through-opening parts H10, H20at the center. A reason thereof is not for causing elastic deformationeasily but for securing an insertion hole which penetrates through therespective through-opening parts H10, H30, H20 of the left side supportbody 10, the annular deformation body 30 and the right side support body20 along the rotation axis (Z axis).

As apparent from the side sectional view of FIG. 3, the basic structuralpart is structured so that the interior thereof is hollow. Where atorque sensor having such a hollow part is used by being incorporatedinto a joint part of a robot arm, a decelerator, etc., can be disposedin the hollow part, thus making it possible to design a space-savingrobot arm on the whole. This is one of the advantages which could not beotherwise obtained by use of a conventional torque sensor which utilizesdistortion of a torsion bar in the shape of a solid round bar.

As described above, in the torque sensor of the prior application, theannular deformation body 30 is required to be constituted of a materialwhich will cause elastic deformation to such an extent as to benecessary for detecting torque. However, the left side support body 10or the right side support body 20 is not required to cause elasticdeformation but rather preferably constituted of a material high inrigidity. In practice, where an insulating material is used as amaterial of the left side support body 10, the right side support body20 or the annular deformation body 30, a synthetic resin such as plasticcan be favorably used. Where a conductive material is used (in thiscase, as will be described below, it is necessary to give insulation toa necessary site for preventing short circuiting of an electrode), ametal such as stainless steel and aluminum can be favorably used. As amatter of course, an insulating material and a conductive material maybe used in combination.

Any of the left side support body 10, the right side support body 20 andthe annular deformation body 30 can be constituted of a flat structuralbody which is small in the thickness in an axial direction, thus makingit possible to set the axial length of an entire sensor so as to beshort. Further, torque is detected only by distortion of the annulardeformation body 30 and, therefore, the annular deformation body 30 isrequired to be made of a material which will cause elastic deformation.Nevertheless, even where it is made of a material relatively high inrigidity, it is possible to perform detection at high accuracy.

<<<Section 2. Principle of Detecting Torque in the Torque Sensor of thePrior Application>>>

Next, here, consideration will be given to how various parts of thetorque sensor are deformed when torque is exerted on the basicstructural part in the torque sensor of the prior application describedin Section 1. FIG. 7 is a sectional view in which the basic structuralpart shown in FIG. 2 is cut along the XY plane, when viewed from theleft side in FIG. 2. The XY coordinate system shown in FIG. 7 is suchthat an ordinary XY coordinate system is viewed from the back (thepositive direction of the X axis is the leftward direction in thedrawing). Therefore, in the XY coordinate system, the upper left domainserves as a first quadrant, the upper right domain serves as a secondquadrant, the lower right domain serves as a third quadrant, and thelower left domain serves as a fourth quadrant. The numbers I to IV shownin the drawing indicate the respective quadrants of the coordinatesystem. The cross sectional part with hatching in the drawingcorresponds to the part of the annular deformation body 30, at the backof which the right side support body 20 can be observed. The points P11to P22 shown in the drawing are orthogonal projection images of therespective connection points P11 to P22 shown in FIG. 4 and FIG. 6 onthe XY plane.

That is, in FIG. 7, the points P11, P12 disposed on the Y axis andindicated by the white dot indicate joined positions (center points ofjoined surfaces) of the protruding parts 11, 12 on the left side supportbody 10, and the points P21, P22 disposed on the X axis and indicated bythe black dot indicate joined positions (center points of joinedsurfaces) of the protruding parts 21, 22 on the right side support body20. As a result, the left side surface of the annular deformation body30 is joined to the left side support body 10 at the connection pointsP11, P12 at two sites along the Y axis, and the right side surface ofthe annular deformation body 30 is joined to the right side support body20 at the connection points P21, P22 at two sites along the X axis.

In the case of the example shown in the drawing, each of the connectionpoints P11, P12, P21, P22 is positioned on a basic annular channel Rindicated by the alternate long and short dashed line in the drawing (acircle positioned between an inner circumference circle and an outercircumference circle of the annular deformation body 30 on the XYplane). As described above, two upper and lower sites of the annulardeformation body 30 are joined to the left side support body 10 and twoleft and right sites thereof are joined to the right side support body20 so that each of the connection points deviates by every 90 degrees,thus making it possible to deform the annular deformation body 30efficiently by exertion of torque.

In the case of the example shown in FIG. 7, where both of the sidesurfaces of the annular deformation body 30 are projected on the XYplane to obtain orthogonal projection images, a projection image of thefirst right side connection point P21 is disposed on the positive Xaxis, a projection image of the second right side connection point P22is disposed on the negative X axis, a projection image of the first leftside connection point P11 is disposed on the positive Y axis and aprojection image of the second left side connection point P12 isdisposed on the negative Y axis. Where these are disposed as describedabove, the annular deformation body 30 can be deformed into anelliptical shape having axial symmetry, by which it is possible toobtain a detection value with axial symmetry.

The torque sensor of the prior application (as with the torque sensoraccording to the present invention) is to detect torque (rotationalmoment) which is applied relatively between the left side support body10 and the right side support body 20 at the basic structural part shownin FIG. 2. And, a detection value thereof indicates a force which isexerted relatively between both support bodies 10, 20. Therefore, here,for the sake of convenience of description, in a state that a load isapplied to the right side support body 20, rotational moment applied tothe left side support body 10 is considered as torque to be detected (asa matter of course, it is also equally valid that in a state that a loadis applied to the left side support body 10, rotational moment appliedto the right side support body 20 is considered as torque to bedetected).

For example, as an example in which the torque sensor is used for ajoint part of a robot arm, consideration is given to an example in whicha drive source such as a motor is mounted on the left side support body10 and a robot hand is mounted on the right side support body 20. If arotational drive force is applied to the left side support body 10 fromthe drive source, with a heavy object grasped by the robot hand, therotational drive force is transmitted to the robot hand via the basicstructural part which constitutes the joint part. In this case, torquewhich will rotationally drive the right side support body 20 is exerted,and the torque corresponds to rotational moment applied to the left sidesupport body 10 in a state that the right side support body 20 is fixed.

Next, consideration is given to a change in the structural body shown inFIG. 7 by the rotational moment. When the right side support body 20 isfixed, the positions of the connection points P21, P22 (black dots) onthe X axis shown in FIG. 7 are in a fixed state. On the other hand, ifrotational moment is applied to the left side support body 10, forexample, in the clockwise direction in FIG. 7, the connection pointsP11, P12 (white dots) on the Y axis attempt to move clockwise. Next, itis inevitable that apart of circular arcs P21 to P11 positioned at thefirst quadrant I undergoes inward contraction, a part of circular arcsP11 to P22 positioned at the second quadrant II undergoes outwardexpansion, a part of circular arc P22 to P12 positioned at the thirdquadrant III undergoes inward contraction and a part of circular arc P12to P21 positioned at the fourth quadrant IV undergoes outward expansion.

FIG. 8 is a sectional view which shows a state that the above-describeddeformation has occurred in the structural body shown in FIG. 7. Thatis, this is a sectional view in which upon exertion of torque which ispositive rotation around the Z axis on the basic structural part shownin FIG. 2, the basic structural part is cut along the XY plane, whenviewed from the left side in FIG. 2. In the present application, withregard to any given coordinate axis, a rotating direction at which aright-hand screw is allowed to advance in the positive direction of thecoordinate axis concerned is defined as a positive direction, whereas arotating direction at which the right-hand screw is allowed to advancein the negative direction of the coordinate axis concerned is defined asa negative direction. Therefore, in FIG. 8, torque which is positiverotation around the Z axis is torque which is exerted in the clockwisedirection, as indicated by the outlined arrow in the drawing.

The broken line given in FIG. 8 indicates a state before deformation ofthe annular deformation body 30 (a state given in FIG. 7). Withreference to the broken line, it can be easily understood that torquewhich is positive rotation around the Z axis is exerted, by which theannular deformation body 30 is deformed into an elliptical shape. Here,for the sake of convenience of description, the V axis and the W axiswhich pass through the origin O and give 45 degrees with respect to theX axis and the Y axis are defined on the XY plane. The V axis is acoordinate axis in which the first quadrant I is given as the positivedirection, and the W axis is a coordinate axis in which the secondquadrant II is given as the positive direction. As shown in the drawing,the annular deformation body 30 is deformed into an elliptical shapehaving a short-axis direction along the V axis and a long-axis directionalong the W axis, giving axial symmetry with respect to the V axis andthe W axis. This axial symmetry is favorable in obtaining a detectionvalue of torque according to a method which is to be described inSection 3.

In the embodiment shown in the drawing, deformation giving axialsymmetry occurs because as shown in FIG. 7, the annular deformation body30 is formed in a perfect circular shape, with no load applied (when notorque is exerted). And, where both side surfaces of the annulardeformation body 30 are projected on the XY plane to obtain orthogonalprojection images, a projection image of the first right side connectionpoint P21 is disposed on the positive X axis, a projection image of thesecond right side connection point P22 is disposed on the negative Xaxis, a projection image of the first left side connection point P11 isdisposed on the positive Y axis, and a projection image of the secondleft side connection point P12 is disposed on the negative Y axis.

The greater the exerted torque, the more the annular deformation body 30is deformed into a flatter elliptical shape. Therefore, in FIG. 8, if adistance of a part of the annular deformation body 30 positioned on theV axis from the origin O and a distance of a part of the annulardeformation body 30 positioned on the W axis from the origin O can bemeasured (these distances serve as information indicating displacementamount from the position before deformation indicated by the brokenline), it is possible to determine the magnitude of the exerted torque.In other words, it is sufficient to measure displacement of the annulardeformation body 30 in the radial direction of the inner circumferentialsurface or the outer circumferential surface.

On the other hand, where torque is exerted reversely, that is, uponexertion of torque which is negative rotation around the Z axis,contrary to the example shown in FIG. 8, a counterclockwise rotationalforce is exerted on the annular deformation body 30 (the connectionpoints P11, P12 thereof). Therefore, the annular deformation body 30 isdeformed into an elliptical shape having a long-axis direction along theV axis and a short-axis direction along the W axis. Thus, apart of theannular deformation body 30 positioned on the V axis or a part thereofpositioned on the W axis undergoes displacement in a direction which isreverse to that of the example shown in FIG. 8.

Consequently, in the torque sensor of the prior application,displacement is measured at the part of the annular deformation body 30positioned on the V axis or the part thereof positioned on the W axis,thus making it possible to detect both the direction and magnitude ofexerted torque. For example, where there is monitored a position atwhich the inner circumferential surface of the annular deformation body30 intersects with the V axis, it can be judged that torque which ispositive rotation around the Z axis is exerted upon inward displacementfrom a reference position indicated by the broken line and torque whichis negative rotation around the Z axis is exerted upon outwarddisplacement. Alternatively, where there is monitored a position atwhich the inner circumferential surface of the annular deformation body30 intersects with the W axis, it is judged that torque which ispositive rotation around the Z axis is exerted upon outward displacementfrom the reference position indicated by the broken line and torquewhich is negative rotation around the Z axis is exerted upon inwarddisplacement. As a matter of course, an absolute value of displacementamount is to indicate the magnitude of the exerted torque.

In the torque sensor of the prior application, the annular deformationbody 30 undergoes relatively great radial displacement depending on theradius of the annular deformation body, despite a small torsion angleoccurring at the annular deformation body 30. Accordingly, even if thereis used an annular deformation body 30 relatively high in rigidity, itis possible to detect torque at sufficient sensitivity.

There has been described above the principle of detecting torque in thetorque sensor of the prior application. In the torque sensor of theprior application, a capacitive element and a detection circuit are alsoadded to the basic structural part described above in order to detecttorque on the basis of the above-described principle.

<<<Section 3. Detection Method by Using Capacitive Elements in theTorque Sensor of the Prior Application>>>

In the torque sensor of the prior application, a capacitive element anda detection circuit are also added to the basic structural part shown inFIG. 2, thereby constituting the torque sensor. As shown in FIG. 8, theannular deformation body 30 is deformed into an elliptical shape byexertion of torque. The part which undergoes displacement to thegreatest extent resulting from the above deformation is a partpositioned on the V axis or a part positioned on the W axis. Therefore,in order to measure an extent of deformation (magnitude of exertedtorque) of the annular deformation body 30 on the basis of displacementof a specific part of the annular deformation body 30, it is mostefficient to measure displacement of the part positioned on the V axisor the part positioned on the W axis.

Thus, in the torque sensor of the prior application, a displacementelectrode is formed at the part positioned on the V axis and the partpositioned on the W axis on an inner circumferential surface of theannular deformation body 30. FIG. 9 is a plan view which shows theannular deformation body 30 in a state that displacement electrodes E31,E32 are formed on the inner circumferential surface, when viewed fromthe left side in FIG. 2. For the sake of convenience of description, theX, Y, Z, V, and W axes are drawn in an overlapped manner. Thedisplacement electrode E31 is an electrode which is formed at a positionat which a positive domain of the V axis intersects with the innercircumferential surface of the annular deformation body 30, and thedisplacement electrode E32 is an electrode which is formed at a positionat which a positive domain of the W axis intersects with the innercircumferential surface of the annular deformation body 30. The depthdimension of each of the displacement electrodes E31, E32, (thedimension in a direction perpendicular to the sheet surface in FIG. 9)is equal to the depth dimension of the annular deformation body 30. Inthe case of this example, the displacement electrodes E31, E32 areconstituted on the inner circumferential surface of the annulardeformation body 30 with a conductive layer such as a metal film formedby a method such as vapor deposition and plating. As a matter of course,where the annular deformation body 30 is made of a metal such asaluminum or stainless steel, the annular deformation body 30 itself haselectrical conductivity. Thus, it is necessary to form the displacementelectrodes E31, E32 via an insulating layer.

On the other hand, fixed electrodes E21, E22 are provided at respectivepositions which oppose the displacement electrodes E31, E32 and fixed tothe right side support body 20. FIG. 10 is a plan view which shows theright side support body 20 in a state that the fixed electrodes E21, E22are mounted, when viewed from the left side in FIG. 2. Also here, forthe sake of convenience of description, the X, Y, V, and W axes aredrawn in an overlapped manner. The fixed electrode E21 is disposed atthe positive domain of the V axis, opposing the displacement electrodeE31. The fixed electrode E22 is disposed at the positive domain of the Waxis, opposing the displacement electrode E32.

FIG. 11 is a side view of the right side support body 20 shown in FIG.10. As shown in the drawing, the fixed electrode E22 is constituted of aconductive plate protruding from the left side surface of the right sidesupport body 20 in a direction along the rotation axis (the negativedirection of the Z axis). The fixed electrode E21 is hidden behind thefixed electrode E22 and therefore does not appear in FIG. 11.

FIG. 12 is a side sectional view in which a structural body having adisplacement electrode and a fixed electrode added to the basicstructural part shown in FIG. 3 is cut along the VZ plane. FIG. 3 is aside sectional view in which the structure body is cut along the YZplane, whereas FIG. 12 is a side sectional view in which it is cut alongthe VZ plane. Therefore, the upside of FIG. 12 is not the direction ofthe Y axis but the direction of the V axis shown in FIG. 9 and FIG. 10.In the side sectional view of FIG. 12, it is clearly shown that thedisplacement electrode E31 and the fixed electrode E21 disposed on the Vaxis are in a state opposing each other. The displacement electrode E31is an electrode which is firmly fixed to the inner circumferentialsurface of the annular deformation body 30 and, therefore, causesdisplacement depending on deformation of the annular deformation body30. On the other hand, the fixed electrode E21 is fixed at its right endto the right side support body 20 and always keeps a constant position,despite deformation of the annular deformation body 30.

Consequently, a relative position of the displacement electrode E31 inrelation to the fixed electrode E21 is changed depending on deformationof the annular deformation body 30. In other words, a distance betweenthe displacement electrode E31 and the fixed electrode E21 is changeddepending on deformation of the annular deformation body 30. Althoughnot shown in FIG. 12, a relationship between the displacement electrodeE32 and the fixed electrode E22 disposed on the W axis is also exactlythe same as the above-described relationship.

FIG. 13 is a sectional view in which the structural body having theabove-described displacement electrodes and the fixed electrodes addedto the basic structural part shown in FIG. 2 is cut along the XY plane,when viewed from the left side in FIG. 2. In this sectional view, thereis clearly shown a state in which the displacement electrode E31 andfixed electrode E21 disposed on the V axis oppose each other and thedisplacement electrode E32 and the fixed electrode E22 disposed on the Waxis oppose each other.

In the case of the example shown here, the displacement electrodes E31,E32 are each constituted of a conductive layer formed on the innercircumferential surface of the annular deformation body 30 and,therefore, the surface thereof is formed as a curved surface along theinner circumference of the annular deformation body 30. Thus, the fixedelectrodes E21, E22 which oppose thereto are also provided aselectrodes, the surfaces of which are curved. In other words, thesurface of each of the displacement electrodes E31, E32 and the fixedelectrodes E21, E22 is constituted of a concentric cylindrical surface,with the Z axis given as the central axis. Of course, each of theelectrodes may be formed in any surface shape, as long as it can play arole of constituting a capacitive element. Therefore, there may be useda flat plate-shaped electrode, the surface of which is planar.

In the drawings of the present application, for the sake of convenienceof illustration, each of the displacement electrodes and each of thefixed electrodes are depicted, with actual thickness dimensionsdisregarded. For example, where the displacement electrodes E31, E32 areconstituted of a conductive layer (vapor deposition layer or platinglayer) on the inner circumferential surface of the annular deformationbody 30, their thickness can be set to the order of a few micrometers.In contrast, where the fixed electrodes E21, E22 are constituted of aconductive plate (metal plate) protruding from the left side surface ofthe right side support body 20, it is preferable that their thickness isset to the order of a few millimeters in order to secure the strength inpractical use. Therefore, in FIG. 13, etc., for the sake of convenience,the displacement electrodes and the fixed electrodes are depicted so asto be equal in thickness. However, actual thickness dimensions of theseelectrodes should be each set to an appropriate value, withconsideration given to a production process and strength in practicaluse.

FIG. 14 is a sectional view on the XY plane which shows a state whentorque which is positive rotation around the Z axis is exerted on thebasic structural part shown in FIG. 13. As described in Section 2, uponexertion of the torque, the annular deformation body 30 is deformed intoan elliptical shape, and the V axis is in a short-axis direction of theellipse, while the W axis is in a long-axis direction of the ellipse. Asa result, the electrode interval between the pair of electrodes E21, E31disposed on the V axis is decreased, and the electrode interval betweenthe pair of electrodes E22, E32 disposed on the W axis is increased.Thus, a capacitive element C1 is constituted of the pair of electrodesE21, E31 and a capacitive element C2 is constituted of the pair ofelectrodes E22, E32, thus making it possible to detect the direction andmagnitude of the exerted torque as the amount of fluctuation incapacitance value of the capacitive elements C1, C2.

For example, when focus is given to the fluctuation in capacitance valueof the capacitive element C1 constituted of the electrodes E21, E31 withreference to an unloaded state (a state where no torque is exerted)shown in FIG. 13, upon exertion of torque which is positive rotationaround the Z axis as shown in FIG. 14, the electrode interval isdecreased to result in an increase in capacitance value. In contrast,upon exertion of torque which is negative rotation around the Z axis,the electrode interval is increased to result in a decrease incapacitance value. Therefore, the increased fluctuation in capacitancevalue indicates exertion of torque which is positive rotation around theZ axis, and the decreased fluctuation in capacitance value indicatesexertion of torque which is negative rotation around the Z axis. As amatter of course, an absolute value of the amount of fluctuationindicates the magnitude of the exerted torque.

Similarly, when focus is given to the fluctuation in capacitance valueof the capacitive element C2 constituted of the electrodes E22, E32,upon exertion of torque which is positive rotation around the Z axis asshown in FIG. 14, the electrode interval is increased to result in adecrease in capacitance value. In contrast, upon exertion of torquewhich is negative rotation around the Z axis, the electrode interval isdecreased to result in an increase in capacitance value. Therefore, thedecreased fluctuation in capacitance value indicates exertion of torquewhich is positive rotation around the Z axis. The increased fluctuationin capacitance value indicates exertion of torque which is negativerotation around the Z axis. As a matter of course, an absolute value ofthe amount of fluctuation indicates the magnitude of the exerted torque.

Consequently, torque around the Z axis can be detected by using thecapacitive element C1 and also by using the capacitive element C2.Theoretically, such detection can be made by using only one of thecapacitive elements. However, in practice, it is preferable thatdetection is made by using both of the capacitive elements C1, C2. Thatis, if the capacitive elements C1, C2 are provided respectively at theshort-axis position (on the V axis) and the long-axis position (on Waxis) upon deformation of the annular deformation part 30 into anelliptical shape, the electrode interval is decreased upon exertion ofthe same torque to result in an increase in capacitance value at theshort-axis position (on the V axis), whereas the electrode interval isincreased to result in a decrease in capacitance value at the long-axisposition (on the W axis). Therefore, it is possible to detect theexerted torque as a difference in both capacitance values C1, C2. Thedifference detection is effective in performing stable torque detectionin which common-mode noise and zero-point drift are suppressed. Thisalso sets off the influences of dilation at various parts due totemperatures, thereby contributing to obtaining a detection value highin accuracy.

In order to perform the above-described difference detection, in short,it will be sufficient that, of individual parts of the annulardeformation body 30, there are provided a first displacement electrodeE31 fixed to a first part (in this example, an intersecting part withthe V axis) which undergoes displacement in a direction moving close tothe rotation axis, a second displacement electrode E32 fixed to a secondpart (in this example, an intersecting part with the W axis) whichundergoes displacement in a direction moving away from the rotation axisupon exertion of torque in a predetermined rotating direction, a firstfixed electrode E21 disposed at a position which opposes the firstdisplacement electrode E31, and a second fixed electrode E22 disposed ata position which opposes the second displacement electrode E32.

Next, as a detection circuit for performing the difference detection, itwill be sufficient that there is provided a circuit which outputs anelectric signal corresponding to a difference between a capacitancevalue of the first capacitive element C1 constituted of the firstdisplacement electrode E31 and the first fixed electrode E21 and acapacitance value of the second capacitive element C2 constituted of thesecond displacement electrode E32 and the second fixed electrode E22 asan electric signal indicating the exerted torque.

As described above, the torque sensor of the prior application can beconstituted by adding displacement electrodes and fixed electrodes tothe simple basic structural part shown in FIG. 1, thus making itpossible to provide a sensor which is small in size and high inrigidity. However, in terms of commercial mass-production, a greatworkload is needed for mounting the fixed electrodes and adjusting theirpositions, thereby posing such problems as reduction in productionefficiency and increase in costs.

In the case of the example shown in FIG. 10, for example, the fixedelectrodes E21, E22 are mounted on the right side support body 20 andrequired to be disposed at positions corresponding to the displacementelectrodes E31, E32 mounted on the inner circumferential surface of theannular deformation body 30. That is, in actuality, as shown in FIG. 11,the fixed electrode E22 is required to be mounted so as to protrude tothe left side in the perpendicular direction from the left side surfaceof the right side support body 20 and to be adjusted so that theopposing electrodes are both parallel to each other (in the case of theexample shown in the drawing, it is required to be mounted so as to giveexactly 90 degrees to the left side surface of the right side supportbody 20). Therefore, in order to fix the base end of the fixed electrodeE22 exactly to the right side support body 20, there is needed atime-consuming step in its own way.

Further, as apparent from the side sectional view of FIG. 12, anelectrode interval between the displacement electrode E31 and the fixedelectrode E21 changes depending on a fixed state of the base end of thefixed electrode E21, and a detection value (a capacitance value of thecapacitive element) will be influenced by the change. Therefore, interms of commercial mass-production, it is necessary to adjust exactlythe position of the fixed electrode E21 for each product, resulting in agreat workload. Further, in order to perform the above-describeddifference detection, a plurality of capacitive elements are required tobe disposed symmetrically and adjusted so that these are individuallyequal in electrode interval, which also results in an additionalincrease in workload.

The present invention is to provide a new device capable of furtherenhancing the production efficiency in order to solve theabove-described problems found in the torque sensor of the priorapplication. Hereinafter, a detailed description will be given of thepresent invention on the basis of specific embodiments.

<<<Section 4. Basic Structural Part of Torque Sensor According to theBasic Embodiment of the Present Invention>>>

<4-1. Overall Constitution of Basic Structural Part>

FIG. 15 is an exploded perspective view which shows a basic structuralpart of a torque sensor according to a basic embodiment of the presentinvention. As shown in the drawing, the basic structural part isconstituted by disposing an annular deformation body 50 between a leftside support body 10 and a right side support body 20 and joining thesethree constituents to each other. Also here, for the sake ofconvenience, as shown in the drawing, an XYZ three-dimensionalcoordinate system is defined to give the following description. The Zaxis drawn in the horizontal direction of the drawing corresponds to arotation axis of torque to be detected, and the torque sensor hasfunctions to detect torque around the rotation axis (around the Z axis).

The basic structural part of the torque sensor of the prior applicationshown in FIG. 1 is different from the basic structural part of thetorque sensor according to the present invention shown in FIG. 15 inthat the annular deformation body 30 of the former is replaced by anannular deformation body 50 of the latter. The annular deformation body30 shown in FIG. 1 is a circular annular member which is obtained byforming the through-opening part H30 smaller in diameter in the shape ofa concentric disk at the center of the disk disposed, with the Z axis(rotation axis) given as the central axis. In contrast, the annulardeformation body 50 shown in FIG. 15 is a member obtained by impartingpartial material-removal processing to the circular annular deformationbody 30, and the rotation axis (Z axis) is inserted through athrough-opening part H60 formed in the interior thereof. Therefore, theannular deformation body 50 is basically a circular annular member inwhich the concentric disk-shaped through-opening part H50 is formed.Detection parts D1 to D4 shown in the drawing are formed by parts towhich the material-removal processing is imparted.

It is noted that here, in order to describe the shape of the annulardeformation body 50, the term “material-removal processing” is used. Inactually preparing the annular deformation body 50, cutting, etc., isnot necessarily imparted to the circular annular member. For example,where the annular deformation body 50 is constituted of a metal, it canbe manufactured by molding with a casting mold. Where the annulardeformation body 50 is constituted of a resin such as plastic, it can bemanufactured by injection molding or pressing by use of a predeterminedmold.

Here, of the annular deformation body 50, parts other than the detectionparts D1 to D4 are referred to as coupling parts L1 to L4. As shown inthe drawing, the annular deformation body 50 is structured so that thefour sets of detection parts D1 to D4 and the four sets of couplingparts L1 to L4 are alternately disposed. The four sets of coupling partsL1 to L4 are each constituted of a circular arc-shaped part of thecircular annular member, and the four sets of detection parts D1 to D4are, as will be described below, structured so as to cause elasticdeformation by exertion of torque. In the case of the example shown inthe drawing, the parts of the detection parts D1 to D4 of the annulardeformation body 50 are each constituted of a plate-shaped piece thin inthickness and the plate-shaped piece functions as a leaf spring, therebycausing elastic deformation by exertion of torque to be detected.

The left side support body 10 and the right side support body 20 shownin FIG. 15 are constituents which are identical to the left side supportbody 10 and the right side support body 20 shown in FIG. 1. These arecircular annular members obtained by forming the through-opening partsH10, H20, each of which is smaller in diameter and formed in the shapeof a concentric disk, at the center of the disk disposed, with the Zaxis (rotation axis) given as the central axis. Consequently, in thecase of the basic structural part shown in FIG. 15 as well, the leftside support body 10 and the right side support body 20 are annularstructural bodies which are respectively provided with through-openingparts H10, H20 at the center. And, there is secured an insertion holewhich penetrates through the respective through-opening parts H10, H50,H20 of the left side support body 10, the annular deformation body 50and the right side support body 20 along the Z axis (rotation axis). Incarrying out the present invention, it is not essentially necessary thatthe through-opening parts H10, H20 are formed respectively on thesupport bodies 10, 20. Therefore, it is not always necessary to providethe through-opening parts H10, H20.

In the basic structural part shown in FIG. 15 as well, the left sidesupport body 10 is a member which supports the left side surface of theannular deformation body 50, and the right side support body 20 is amember which supports the right side surface of the annular deformationbody 50. Also here, the origin O of the XYZ three-dimensional coordinatesystem is defined at the center position of the annular deformation body50. Any of the left side support body 10, the annular deformation body50 and the right side support body 20 is disposed so that the Z axis isgiven as the central axis.

Further, two fan-shaped protruding parts 11, 12 protruding to the rightside (left side connection members) are provided on the right sidesurface of the left side support body 10, and top surfaces of theprotruding parts 11, 12 are joined to the left side surface of theannular deformation body 50. Similarly, two fan-shaped protruding parts21, 22 protruding to the left side (right side connection members) areprovided on the left side surface of the right side support body 20, andtop surfaces of the protruding parts 21, 22 are joined to the right sidesurface of the annular deformation body 50.

As shown in the drawing, the protruding part 11 is joined to an upperside of the annular deformation body 50 (the coupling part L2 positionedin the positive direction of the Y axis), whereas the protruding part 12is joined to a lower side of the annular deformation body 50 (thecoupling part L4 positioned in the negative direction of the Y axis).Similarly, the protruding part 21 is joined to a far part of the annulardeformation body 50 (the coupling part L1 positioned in the positivedirection of the X axis), whereas the protruding part 22 is joined to anear part of the annular deformation body 50 (the coupling part L3positioned in the negative direction of the X axis). As will bedescribed below, the connection positions of these protruding partsrespectively correspond to the positions of connection points Q1 to Q4of the annular deformation body 50.

FIG. 16 is a side view which shows the basic structural part of thetorque sensor obtained by joining the three constituents shown in FIG.15 to each other (to avoid making the drawing complicated, as for thedetection parts, there are indicated only the outer circumferentialsurfaces of the detection parts D2, D3 positioned forward). In the caseof the example shown here, as shown in FIG. 15, the protruding parts 11,12 are structural bodies formed integrally with the left side supportbody 10, and the top surfaces thereof are joined to the left sidesurfaces of the coupling parts L2, L4 of the annular deformation body50. Similarly, the protruding parts 21, 22 are structural bodies formedintegrally with the right side support body 20, and the top surfacesthereof are joined to the right side surfaces of the coupling parts L1,L3 of the annular deformation body 50.

Consequently, the protruding parts 11, 12 function as the left-sideconnection members which connect left side connection points on the leftside surface of the annular deformation body 50 which opposes the leftside support body 10 with the left side support body 10. The protrudingparts 21, 22 function as the right-side connection members which connectright side connection points on the right side surface of the annulardeformation body 50 which opposes the right side support body 20 withthe right side support body 20.

FIG. 17 is a front view which shows the annular deformation body 50shown in FIG. 15, when viewed from the right side in FIG. 15. In thisdrawing as well, for the sake of convenience of description, the V axisand the W axis which pass through the origin O and give 45 degrees withrespect to the X axis and the Y axis are defined on the XY plane. The Vaxis is a coordinate axis in which the X axis is rotatedcounterclockwise by 45 degrees on the XY plane, with the origin O givenas the center. The W axis is a coordinate axis in which the Y axis isrotated counterclockwise by 45 degrees on the XY plane, with the originO given as the center. As shown in the drawing, the first detection partD1 is disposed on the positive V axis (first quadrant I), the seconddetection part D2 is disposed on the positive W axis (second quadrantII), the third detection part D3 is disposed on the negative V axis(third quadrant III) and the fourth detection part D4 is disposed on thenegative W axis (fourth quadrant IV).

Here, each of the detection parts D1 to D4 is constituted of threecomponents composed of a first deformation part 51, a second deformationpart 52 and a displacement part 53. In the drawing, reference symbolsare given only to components which constitute the detection part D1. Thedetection parts D2 to D4 are also constituted in the same manner. Athree dimensional configuration of the four sets of detection parts D1to D4 is as shown in the exploded perspective view of FIG. 15. Four setsof coupling parts L1 to L4 have functions of coupling the four sets ofdetection parts D1 to D4. And, the coupling parts L1 to L4 arerespectively placed between each of the detection parts D1 to D4.

In FIG. 17, joined positions of the protruding parts 11, 12 (left sideconnection members) and joined positions of the protruding parts 21, 22(right side connection members) are indicated by the broken lines.

FIG. 18 is a projection view on the XY plane which indicates adisposition of the individual detection points Q1 to Q4 and theindividual connection points P11 to P22 on the annular deformation body50 shown in FIG. 15 (a drawing viewed from the right side support body20). The annular deformation body 50 is indicated only for a projectionimage formed by internal and external contour circles. Further, a thickcircle depicted by the alternate long and short dashed line in thedrawing is a basic annular channel R defined on the XY plane. In thecase of the example shown in the drawing, the basic annular channel R isa circle on the XY plane which passes through an intermediate positionbetween an internal contour circle of the annular deformation body 50and an external contour circle thereof, and this is the center line ofan annular thick part of the annular deformation body 50.

As shown in the drawing, four sets of the detection points Q1 to Q4 aredefined as points on the basic annular channel R. Specifically, a firstdetection point Q1 is defined at a position at which the positive V axisintersects with the basic annular channel R, a second detection point Q2is defined at a position at which the positive W axis intersects withthe basic annular channel R, a third detection point Q3 is defined at aposition at which the negative V axis intersects with the basic annularchannel R, and a fourth detection point Q4 is defined at a position atwhich the negative W axis intersects with the basic annular channel R.The detection points Q1 to Q4 indicate the respective dispositions ofthe detection parts D1 to D4. That is, FIG. 17 is compared with FIG. 18to understand that the first detection part D1 is disposed at a positionof the first detection point Q1, the second detection part D2 isdisposed at a position of the second detection point Q2, the thirddetection part D3 is disposed at a position of the third detection pointQ3, and the fourth detection part D4 is disposed at a position of thefourth detection point Q4.

On the other hand, points P11, P12 indicated by the white dot in FIG. 18are projection images of the left side connection points, and pointsP21, P22 indicated by the black dot in FIG. 18 are projection images ofthe right side connection points. As described above, the left sideconnection points P11, P12 are in actuality points on the left sidesurface of the annular deformation body 50, indicating the connectionpositions of the protruding parts 11, 12 (left side connection members).The right side connection points P21, P22 are in actuality points on theright side surface of the annular deformation body 50, indicating theconnection positions of the protruding parts 21, 22 (right sideconnection members). In the case of the example shown in the drawing,projection images of these connection points P11 to P22 are alsopositioned on the basic annular channel R. That is, the projectionimages of the left side connection points P11, P12 are each defined at aposition at which the Y axis intersects with the basic annular channelR, and the projection images of the right side connection points P21,P22 are each defined at a position at which the X axis intersects withthe basic annular channel R.

Consequently, in the case of the example shown in FIG. 18, the left sideconnection points P11, P12 (white dots) indicating the connectionpositions of the left side connection members 11, 12 and the right sideconnection points P21, P22 (black dots) indicating the connectionpositions of the right side connection members 21, 22 are alternatelydisposed along the basic annular channel R. This alternate dispositionis, as will be described below, important in causing effectivedeformation in the annular deformation body 50 upon exertion of torqueto be detected. Further, four sets of the detection points Q1 to Q4 aredisposed individually between the connection points P11 to P22. Thisdisposition is also important in causing effective displacement at therespective detection parts D1 to D4 upon exertion of torque to bedetected.

<4-2. Structure and Function of Detection Part>

Next, a description will be given of a structure and function of each ofthe detection parts D1 to D4. FIG. 19 is a partial sectional view whichshows a detailed structure of the detection parts D1 to D4 of theannular deformation body 50 shown in FIG. 15. The four sets of detectionparts D1 to D4 are identical in structure to each other. The detectionpart D shown in FIG. 19 represents the four sets of detection parts D1to D4, showing a cross sectional part in which the annular deformationbody 50 is cut along a cylindrical surface including the basic annularchannel R. FIG. 19(a) indicates a state that no torque is exerted. FIG.19(b) indicates a state that a compressive force f1 is exerted on thedetection part D by exertion of torque. FIG. 19(c) indicates a statethat an extension force f2 is exerted on the detection part D byexertion of torque.

As shown in FIG. 19(a), a coupling part L is positioned both on the leftand right sides of the detection part D. The coupling part L correspondsto any one of the four sets of coupling parts L1 to L4. For example,where the detection part D shown in FIG. 19(a) is the second detectionpart D2 shown in FIG. 15, the coupling part L disposed on the right-handside corresponds to the coupling part L2 shown in FIG. 15. The couplingpart L disposed on the left-hand side corresponds to the coupling partL3 shown in FIG. 15.

As shown in the drawing, the detection part D is provided with a firstdeformation part 51 which causes elastic deformation by exertion oftorque to be detected, a second deformation part 52 which causes elasticdeformation by exertion of torque to be detected, and a displacementpart 53 which causes displacement resulting from elastic deformation ofthe first deformation part 51 and the second deformation part 52. And,it is disposed between an end portion of the coupling part L disposed onthe left-hand side and an end portion of the coupling part L disposed onthe right-hand side.

In the example shown here, the first deformation part 51 is constitutedof a first plate-shaped piece which has flexibility, the seconddeformation part 52 is constituted of a second plate-shaped piece whichhas flexibility, and the displacement part 53 is constituted of a thirdplate-shaped piece. In actuality, the annular deformation body 50 isconstituted of a structural body made of the same material such as ametal (stainless steel or aluminum) and a synthetic resin (such asplastic). The first plate-shaped piece 51, the second plate-shaped piece52 and the displacement part 53 are each a plate-shaped member thinnerin thickness than the coupling part L and, therefore, have flexibility.

In the case of the example shown here, the displacement part 53 is alsoa plate-shaped member thinner in thickness and, therefore, hasflexibility. However, the displacement part 53 is not necessarily amember which has flexibility (as a matter of course, it may haveflexibility). The displacement part 53 plays a role of causingdisplacement to the opposing right side support body 20 upon exertion oftorque. And in order to cause the displacement, it will be sufficientthat the first deformation part 51 and the second deformation part 52have flexibility. Therefore, the displacement part 53 is not necessarilyconstituted of a plate-shaped member thinner in thickness but may be amember thicker in thickness. On the other hand, the coupling part L mayhave certain flexibility. However, in order to cause effectivedeformation to the first deformation part 51 and the second deformationpart 52 by exertion of torque, it is preferable that the coupling part Ldoes not undergo deformation to the minimum extent possible.

An external end of the first deformation part 51 is connected to acoupling part L adjacent thereto and an internal end of the firstdeformation part 51 is connected to the displacement part 53. Further,an external end of the second deformation part 52 is connected to acoupling part L adjacent thereto and an internal end of the seconddeformation part 52 is connected to the displacement part 53. In thecase of the example shown in FIG. 19 (a), the first deformation part,the second deformation part and the displacement part are constitutedrespectively with the first plate-shaped piece 51, the secondplate-shaped piece 52 and the third plate-shaped piece 53. The externalend (left end) of the first plate-shaped piece 51 is connected to aright end portion of the coupling part L disposed on the left-hand side,the internal end (right end) of the first plate-shaped piece 51 isconnected to a left end of the third plate-shaped piece 53. The externalend (right end) of the second plate-shaped piece 52 is connected to aleft end portion of the coupling part L disposed on the right-hand side,and the internal end of the second plate-shaped piece 52 is connected toa right end of the third plate-shaped piece 53.

As described above, the detection part D is disposed at a position ofthe detection point Q defined on the basic annular channel R. The normalline N shown in FIG. 19(a) is a normal line orthogonal to the basicplane (XY plane) including the basic annular channel R provided at aposition of the detection point Q, and the detection part D is disposedso that the normal line N comes to the center. Further, in the sectionalview of FIG. 19 (a), the first plate-shaped piece 51 and the secondplate-shaped piece 52 are inclined to the normal line N and also thefirst plate-shaped piece 51 is inclined (to descend in the rightwarddirection) and the second plate-shaped piece 52 is inclined (to ascendin the rightward direction) so as to be reverse in direction. Inparticular, in the case of the example shown in the drawing, the crosssectional shape of the detection part D gives line symmetry in relationto the normal line N, and both upper and lower surfaces of the thirdplate-shaped piece 53 constitute surfaces parallel to the XY plane.

As described above, with regard to the cross section including the basicannular channel R, the first plate-shaped piece 51 and the secondplate-shaped piece 52 are inclined so as to be reverse in direction inrelation to the normal line N. Therefore, the third plate-shaped piece53 (displacement part) is reverse in the displacement directiondepending on where a compressive force f1 is exerted or where anextension force f2 is exerted in a direction along the basic annularchannel R. As will be described below, this is favorable in performingdifference detection by using a plurality of capacitive elements.

That is, as shown in FIG. 19(b), where a compressive force f1 (indicatedby the outlined arrow in the drawing) is exerted on the detection part Din a direction along the basic annular channel R, stress is applied tothe detection part D in a direction at which the breadth is decreased.Therefore, postures of the first plate-shaped piece 51 and the secondplate-shaped piece 52 are changed into a state that is erectedperpendicularly to a greater extent. As a result, the third plate-shapedpiece 53 (displacement part) undergoes downward displacement asindicated by the black arrow in the drawing. On the other hand, as shownin FIG. 19(c), where an extension force f2 (indicated by the outlinedarrow in the drawing) is exerted on the detection part D in a directionalong the basic annular channel R, stress is applied to the detectionpart D in a direction at which the breadth is increased. Therefore,postures of the first plate-shaped piece 51 and the second plate-shapedpiece 52 are changed into a state that these are flattened in thehorizontal direction to a greater extent. Consequently, the thirdplate-shaped piece 53 (the displacement part) undergoes upwarddisplacement as shown by the black arrow in the drawing.

A basic principle of the present invention is to detect the directionand magnitude of exerted torque by using the above-describeddisplacement. That is, the direction of exerted torque can be detectedby the displacement direction of the displacement part 53 (whetherdownward or upward displacement in FIG. 19) and the magnitude of exertedtorque can be detected by the displacement amount thereof.

<4-3. Constitution of Capacitive Element>

In the present invention, a capacitive element is used to detectdisplacement of the displacement part 53. FIG. 20 is a partial sectionalview which shows a detailed structure in which electrodes are providedat the detection parts D1 to D4 of the annular deformation body 50 andpredetermined parts of the right side support body 20 opposing theretoshown in FIG. 15, thereby showing apart of the annular deformation body50 and that of the right side support body 20 shown in FIG. 15. In FIG.20 as well, the four sets of detection parts D1 to D4 are represented bythe detection part D. This figure shows a cross sectional part in whichthe annular deformation body 50 is cut along a cylindrical surfaceincluding the basic annular channel R. That is, a part of the annulardeformation body 50 shown on the left side in FIG. 20 corresponds to apart of the annular deformation body 50 shown in FIG. 19(a).

As described above, in a state that no torque is exerted, both surfacesof the third plate-shaped piece 53 constitute surfaces parallel to theXY plane including the basic annular channel R. Therefore, as shown inthe drawing, the third plate-shaped piece 53 (displacement part) isparallel to an opposing surface of the right side support body 20. Inaddition, in the case of the example shown here, the cross sectionalshape of the detection part D gives line symmetry in relation to thenormal line N, by which the third plate-shaped piece 53 (displacementpart) causes displacement so as to move in parallel along the normalline N, as shown in FIG. 19(b) and FIG. 19(c). As a result, the thirdplate-shaped piece 53 (displacement part) is always kept parallel to theopposing surface of the right side support body 20.

In order to detect displacement of the displacement part, a displacementelectrode E50 is fixed via an insulating layer I50 to a position of thethird plate-shaped piece 53 (displacement part) which opposes the rightside support body 20. Further, a fixed electrode E20 is fixed via aninsulating layer I20 to a position of the right side support body 20which opposes the displacement electrode E50. Then, the displacementdirection and displacement amount of the third plate-shaped piece 53(displacement part) on the basis of a capacitance value of a capacitiveelement C which is constituted of the displacement electrode E50 and thefixed electrode E20 can be detected.

Specifically, as shown in FIG. 19(b), when a compressive force f1 isexerted on the detection part D, a distance between both electrodes isdecreased to increase a capacitance value of the capacitive element C.As shown in FIG. 19(c), when an extension force f2 is exerted on thedetection part D, the distance between both electrodes is increased todecrease a capacitance value of the capacitive element C. FIG. 20 showsan example in which the capacitive element C is formed at the detectionpart D. As a matter of course, in actuality, the displacement electrodeE50 and the fixed electrode E20 are provided at each of the four sets ofdetection parts D1 to D4 shown in FIG. 15, thereby forming four sets ofcapacitive elements C1 to C4. A principle for performing specific torquedetection by using the four sets of capacitive elements C1 to C4 will bedescribed in detail below at Section 5.

It is noted that in the example shown in FIG. 20, the displacementelectrode E50 is fixed via the insulating layer I50 to the thirdplate-shaped piece 53 (displacement part). This is because the annulardeformation body 50 is constituted of a conductive material such as ametal. Similarly, the fixed electrode E20 is fixed via the insulatinglayer I20 to the right side support body 20. This is because the rightside support body 20 is constituted of a conductive material such as ametal. That is, in the case of the example shown here, the left sidesupport body 10, the right side support body 20 and the annulardeformation body 50 are constituted of a conductive material such as ametal. Therefore, the displacement electrode E50 is formed on thesurface of the displacement part 53 via the insulating layer I50, andthe fixed electrode E20 is formed on the surface of the right sidesupport body 20 via the insulating layer I20.

Thus, where the annular deformation body 50 (of which at least a surfaceof forming the displacement electrode E50) is constituted of aninsulating material such as a resin, it is not necessary to provide theinsulating layer I50. Similarly, where the right side support body 20(of which at least a surface of forming the fixed electrode E20) isconstituted of an insulating material such as a resin, it is notnecessary to provide the insulating layer I20.

Further, where the annular deformation body 50 is constituted of aconductive material such as a metal, a certain domain of the surface ofthe right side surface of the annular deformation body 50 can be used asthe displacement electrode E50. For example, in the example shown inFIG. 20, the annular deformation body 50 is constituted of a conductivematerial, by which the third plate-shaped piece 53 (displacement part)is made into an electrically conductive plate. Then, the plate itselfcan function as the displacement electrode E50, thereby eliminating thenecessity for separately providing the displacement electrode E50. Inthis case, in terms of electricity, an entire surface of the annulardeformation body 50 is made equal in potential. However, a part whichactually functions as the displacement electrode E50 of each of the foursets of capacitive elements C1 to C4 is only a domain which opposes eachof the four sets of fixed electrode E20 provided individually.Therefore, each of the four sets of capacitive elements C1 to C4 behavesas a discrete capacitive element, which poses no difficulties inprinciple.

In contrast, where the right side support body 20 is constituted of aconductive material such as a metal, a certain domain of the surface ofthe left side surface of the right side support body 20 can be used asthe fixed electrode E20. For example, in the example shown in FIG. 20,the right side support body 20 is constituted of a conductive material,by which a part of the surface of the left side surface thereof canfunction as the fixed electrode E20. Therefore, there is eliminated thenecessity for separately providing the fixed electrode E20. In thiscase, in terms of electricity, an entire surface of the right sidesupport body 20 is made equal in potential. However, the part whichfunctions as the fixed electrode E20 of each of the four sets ofcapacitive elements C1 to C4 is actually only a domain which opposeseach of four sets of displacement electrodes E50 separately provided.Therefore, each of the four sets of capacitive elements C1 to C4 behavesas a discrete capacitive element, which poses no difficulties inprinciple.

As described above, where the annular deformation body 50 is constitutedof a conductive material such as a metal or where the right side supportbody 20 is constituted of a conductive material such as a metal, thereis removed a step for providing a discrete displacement electrode E50 ora discrete fixed electrode E20, thus making it possible to furtherenhance the production efficiency.

Of course, the above simplified structure gives the annular deformationbody 50 in its entirety or the right side support body 20 in itsentirety as a common electrode, thus resulting stray capacitancegeneration at various parts which are not intended. As a result, adetection value of electrostatic capacitance may be easily mixed withnoise components to decrease the detection accuracy. Thus, in a torquesensor which is required to perform high accuracy detection, even wherethe annular deformation body 50 and the right side support body 20 areconstituted of a conductive material, as with the example shown in FIG.20, it is preferable to provide a discrete displacement electrode E50and a discrete fixed electrode E20 via the respective insulating layers.

It is noted that ease in elastic deformation of the detection part Dserves as a parameter which influences the detection sensitivity of asensor. Use of the detection part D which is more likely to undergoelastic deformation can provide a sensor high in sensitivity and capableof detecting subtle torque, with a maximum value of detectable torquesuppressed. In contrast, use of the detection part D which is lesslikely to undergo elastic deformation is able to increase a maximumvalue of detectable torque but unable to detect subtle torque due todecreased sensitivity.

Ease in elastic deformation of the detection part D is determineddepending on dimensions such as thickness (the thinner, the more easilyelastic deformation will occur) of the first deformation part 51 (thefirst plate-shaped piece) and the second deformation part 52 (the secondplate-shaped piece), the width thereof (the narrower, the more easilyelastic deformation will occur) and the length thereof (the longer, themore easily elastic deformation will occur) and also depending onmaterials thereof. Further, the detection part D can be designed by sucha structure that causes the displacement part 53 (the third plate-shapedpiece) to undergo elastic deformation. Therefore, in practice, it willbe sufficient that dimensions and materials of various parts of thedetection part D may be appropriately selected depending on individualapplications of a torque sensor.

As described above, for the sake of convenience of illustration, thedrawings of the present application are depicted, with actual dimensionsof various parts disregarded. For example, in FIG. 20, the displacementelectrode E50 and the fixed electrode E20 as well as the insulatinglayer I50 and the insulating layer I20 are depicted so as to besubstantially equal in thickness to each of the plate-shaped pieces 51,52, 53. However, these electrodes and the insulating layers can beconstituted by vapor deposition or plating, and the thickness thereofcan be set to the order of a few micrometers. In contrast, it ispreferable that the plate-shaped pieces 51, 52, 53 are designed to begreater in thickness, with practical strength taken into account. It ispreferable that these are set to the order of one mm or so, for example,where these are constituted of a metal.

On the other hand, the left side support body 10 and the right sidesupport body 20 are not required to be a member which causes elasticdeformation according to the principle for detecting torque. Rather, inorder that exerted torque contributes completely to deformation of theannular deformation body 50, the left side support body 10 and the rightside support body 20 are preferably a perfect rigid body. In the exampleshown in the drawing, the reason why the annular structural bodieshaving the through-opening parts H10, H20 at the center are used as theleft side support body 10 and the right side support body 20 is not forcausing easy elastic deformation but for securing an insertion holewhich penetrates through the respective through-opening parts H10, H50,H20 of the left side support body 10, the annular deformation body 50and the right side support body 20 along the rotation axis (Z axis). Aswith the torque sensor of the prior application described in Section 1to Section 3, such a structure is adopted that the interior is hollow,by which various components can be disposed in the hollow part toenhance practical usage.

As shown in FIG. 15, any of the left side support body 10, the rightside support body 20 and the annular deformation body 50 can beconstituted of a flat structural body which is thinner in thickness inthe direction of the Z axis, thus making it possible to set an entireaxial length of the sensor so as to be short. Further, electrodes forconstituting the capacitive element C can be made simple in structure,by which an effect of enhancing the production efficiency can beexpected. The effect can be easily understood by comparing thecapacitive element of the torque sensor of the prior applicationillustrated in FIG. 12 with the capacitive element of the torque sensoraccording to the present invention illustrated in FIG. 20.

That is, in the torque sensor of the prior application illustrated FIG.12, the capacitive element is constituted of the displacement electrodeE31 formed on the inner circumferential surface of the annulardeformation body 30 and the fixed electrode E21 fixed on the left sidesurface of the right side support body 20. Therefore, in order to fix abase end of the fixed electrode E21 exactly to the right side supportbody 20, there is a need for a time-consuming step. Further, a greatamount of workload is needed for adjusting the position thereof,inevitably resulting in a decrease in production efficiency. Inactuality, only a slight positional deviation of the fixed electrode E21at the leading end could cause a fluctuation in distance between thedisplacement electrode E31 and the fixed electrode E21, by which thecapacitive element will fluctuate in capacitance value. This problem isderived from such a disposition of the fixed electrode E21 so as toprotrude from the left side surface of the right side support body 20 tothe left in the perpendicular direction.

On the other hand, in the torque sensor according to the presentinvention illustrated in FIG. 20, the electrodes are all disposed alonga forming surface thereof, by which the above-described problem is notposed. That is, the displacement electrode E50 is a layered electrodewhich is formed along the surface of the displacement part 53, and thefixed electrode E20 is a layered electrode formed along the left sidesurface of the right side support body 20. Since both of them arelayered electrodes disposed along the forming surface, these can beformed by using a generally-accepted film forming step, therebyrelatively reducing a workload in the film forming step.

Further, a clearance between the annular deformation body 50 and theright side support body 20 is regulated by the thickness of theprotruding parts 21, 22 (right side connection members) shown in FIG.15. Therefore, a clearance between the displacement electrode E50 andthe fixed electrode E20 (electrode interval of the capacitive element C)can be accurately adjusted by controlling the thickness of each of theinsulating layer I50, the displacement electrode E50, the fixedelectrode E20 and the insulating layer I20. Use of a generally acceptedfilm forming step makes it possible to control the thickness accurately.Even with commercial production, such adjustment can be easily made thatan electrode opposing thereto is kept parallel to each of the capacitiveelements and also that the plurality of capacitive elements are keptequal in electrode interval to each other. Due to the above-describedreasons, according to the present invention, it is possible to provide atorque sensor which is small in size, high in rigidity and capable ofrealizing high production efficiency.

<<<Section 5. Principle of Detecting Torque by Torque Sensor Accordingto the Basic Embodiment>>>

Next, a description will be given of the principle of detecting torqueby the torque sensor described in Section 4.

<5-1. Detection of Torque by Use of Capacitive Element>

FIG. 21 is a sectional view on the XY plane which shows a deformationstate when torque +Mz which is positive rotation around the Z axis isexerted on the left side support body 10 in a state that load is appliedto the right side support body 20 of the basic structural part shown inFIG. 15. In other words, this is a sectional view in which the basicstructural part shown in FIG. 15 is cut along the XY plane and viewedfrom the right side in FIG. 15. Also here, for the sake of convenienceof description, the V axis and the W axis are defined as coordinate axesin which the X axis and the Y axis are respectively rotatedcounterclockwise by 45 degrees.

A cross sectional part to which hatching is given in the drawingcorresponds to the annular deformation body 50, and the left sidesupport body 10 is seen therebehind. The points P11 to P22 in thedrawing are orthogonal projection images of the respective connectionpoints P11 to P22 on the XY plane. When torque +Mz which is positiverotation around the Z axis is exerted on the left side support body 10,counterclockwise stress indicated by the outlined arrow is exerted onthe points P11, P12 (left side connection points) indicated by the whitedot in the drawing. On the other hand, since load is applied to theright side support body 20, the points P21, P22 (right side connectionpoints) indicated by the black dot in the drawing tend to remain atthese fixed positions.

Consequently, the extension force f2 as indicated by the outlined arrowin the drawing is exerted at the vicinities of positions of a firstdetection point Q1 and a third detection point Q3, and the compressiveforce f1 indicated by the outlined arrow in the drawing is exerted atthe vicinities of positions of a second detection point Q2 and a fourthdetection point Q4. Consequently, the annular deformation body 50 is, asshown in the drawing, deformed into an elliptical shape in which the Waxis is given as a long axis and the V axis is given as a short axis(the broken line in the drawing indicates a state before deformation).

As described above, the detection parts D1 to D4 are disposedrespectively at the detection points Q1 to Q4 to form capacitiveelements C1 to C4. As shown in FIG. 19(b), the displacement part 53 ofthe detection part D on which a compressive force f1 is exertedundergoes displacement so as to move close to the right side supportbody 20, by which the capacitive element C is increased in capacitancevalue. As shown in FIG. 19(c), the displacement part 53 of the detectionpart D on which an extension force f2 is exerted undergoes displacementso as to move away from the right side support body 20, by which thecapacitive element C is decreased in capacitance value. Therefore, whentorque +Mx which is positive rotation around the Z axis is exerted, eachof the detection parts D1 to D4 shows the behavior given in FIG. 22.

That is, when displacement electrodes disposed at the detection parts D1to D4 are respectively given as E501 to E504 and fixed electrodesopposing thereto are respectively given as E201 to E204, an extensionforce f2 is exerted on the detection points Q1, Q3 by exertion of torque+Mz which is positive rotation around the Z axis. Thereby, thedisplacement electrodes E501, E503 undergo displacement so as to moveaway from the fixed electrodes E201, E203, by which the capacitiveelements C1, C3 are decreased in capacitance value (indicated by [−] inthe table). On the other hand, a compressive force f1 is exerted on thedetection points Q2, Q4 and the displacement electrodes E502, E504undergo displacement so as to move close to the fixed electrodes E202,E204, by which the capacitive elements C2, C4 are increased incapacitance value (indicated by [+] in the table).

Therefore, if a capacitance value of each of the capacitive elements C1to C4 is expressed by the same reference symbols C1 to C4, as shown atthe bottom line in the table, computation on the basis of an arithmeticexpression “Mz=−C1+C2−C3+C4” is carried out, thus the exerted torque +Mzwhich is positive rotation around the Z axis can be detected. In thiscase, the thus obtained computation value Mz is a positive value and anabsolute value thereof indicates the magnitude of the exerted torque.

On the other hand, when reversely rotating torque, that is, torque −Mzwhich is negative rotation around the Z axis is exerted, each of thedetection parts D1 to D4 shows behavior which is reverse to that shownin FIG. 22. The compressive force f1 is exerted on the detection pointsQ1, Q3 and the extension force f2 is exerted on the detection points Q2,Q4. Therefore, the capacitive elements C1, C3 are increased incapacitance value, while the capacitive elements C2, C4 are decreased incapacitance value. As a result, the computation value Mz obtained on thebasis of the arithmetic expression “Mz=−C1+C2−C3+C4” is a negative valueand an absolute value thereof indicates the magnitude of the exertedtorque. Consequently, the reference symbol of the computation value Mzobtained by the arithmetic expression indicates the direction of theexerted torque and the absolute value indicates the magnitude thereof.

Also here, for the sake of convenience of description, rotational momentapplied to the left side support body 10 in a state that load is appliedto the right side support body 20 is considered as torque to bedetected. As a matter of course, the principle of detecting torque isexactly applicable also even to a case where rotational moment appliedto the right side support body 20 in a state that a load is applied tothe left side support body 10 is considered as torque to be detected.

Therefore, in the case of the basic embodiment, use of the detectioncircuit shown in the circuit diagram in FIG. 23 enables the torquearound the Z axis to be detected. The E501 to E504 indicated in thecircuit diagram are displacement electrodes provided at the respectivedetection parts D1 to D4, the E201 to E204 are fixed electrodes whichoppose the displacement electrode E501 to E504, and C1 to C4 arecapacitive elements which are constituted of these electrodes. Further,C/V conversion circuits 101 to 104 are circuits for convertingrespectively capacitance values C1 to C4 of the capacitive elements C1to C4 to voltage values V1 to V4. The voltage values V1 to V4 afterconversion are respectively given as values corresponding to thecapacitance values C1 to C4. A difference computing unit 105 functionsto perform computation based on the above-described arithmeticexpression of “Mz=−C1+C2−C3+C4,” thereby outputting the result to anoutput terminal T.

As shown in FIG. 21, when torque around the Z axis is exerted, aposition of each of the detection points Q1 to Q4 undergoes slightdisplacement in a direction along a circumference of the annulardeformation body 50, in response to deformation of the annulardeformation body 50. Specifically, in the case of the example shown inthe drawing, the position of each of the detection points Q1 to Q4 moveto a position deviating slightly from the V axis or the W axis in thecounterclockwise direction. Therefore, upon exertion of torque, thedetection point Q shown in FIG. 20 also moves vertically in the drawing,by which the displacement part 53 (displacement electrode E50) not onlyundergoes lateral displacement in the drawing but also undergoesvertical displacement in the drawing.

However, in the case of the example shown in FIG. 20, the size of thefixed electrode E20 (planner size, that is, occupied area) is set to belarger than the size of the displacement electrode E50 (planner size,that is, occupied area). As a result, even when the displacementelectrode E50 undergoes displacement in the vertical direction in thedrawing or in a direction perpendicular to the sheet surface in thedrawing, no change is found in an opposing area of the displacementelectrode E50 in relation to the fixed electrode E20. Therefore, thecapacitive element C is always kept constant in effective area.

FIG. 24 is a drawing which shows the principle that, as described above,the capacitive element C is kept constant in effective area, even uponchange in relative position of the displacement electrode E50 inrelation to the fixed electrode E20. Now, consideration is given to acase where a pair of electrodes EL, ES is disposed so as to oppose eachother, as shown in FIG. 24(a). Both the electrodes EL, ES are disposedso that these are parallel to each other, with a predetermined clearancekept, thereby constituting a capacitive element. However, the electrodeEL is larger in area than the electrode ES. Where a contour of theelectrode ES is projected on the surface of the electrode EL to form anorthogonal projection image, the projection image of the electrode ES iscompletely included in the surface of the electrode EL. In this case, anarea of the electrode ES is as an effective area as the capacitiveelement.

FIG. 24(b) is a side view which shows the pair of electrodes ES, ELgiven in FIG. 24(a). The domain to which hatching is given in thedrawing is a part which substantially functions as a capacitive elementand the effective area as the capacitive element is an area of theelectrode to which hatching is given (that is, an area of the electrodeES).

Now, consideration is given to a perpendicular surface U indicated bythe alternate long and short dashed line in the drawing. The electrodesES, EL are both disposed so as to be parallel to the perpendicularsurface U. Here, on the assumption that the electrode ES is allowed tomove along the perpendicular surface U perpendicularly upward, anopposing part of the electrode EL moves upward but the opposing partconcerned remains unchanged in area. Even if the electrode ES is allowedto move downward or move backward or forward on the sheet surface, theopposing part of the electrode EL side also remains unchanged in area.

In short words, where the contour of the electrode ES smaller in area isprojected on the surface of the electrode EL larger in area to form anorthogonal projection image, as long as the projection image of theelectrode ES is kept included completely within the surface of theelectrode EL, the effective area of the capacitive element constitutedof both the electrodes is equal to an area of the electrode ES andalways kept constant.

Therefore, if a relationship between the displacement electrode E50 andthe fixed electrode E20 shown in FIG. 20 is similar to a relationshipbetween the electrode ES and the electrode EL shown in FIG. 24,irrespective of a direction at which the displacement electrode E50undergoes displacement by exertion of torque, as long as thedisplacement electrode E50 and the fixed electrode E20 are kept parallelto each other, the pair of electrodes which constitute the capacitiveelement are constant in effective opposing area. This means that thecapacitive element C is changed in capacitance value exclusivelydepending on a distance between the displacement electrode E50 and thefixed electrode E20. In other words, this means that a change incapacitance value of the capacitive element C occurs only depending ondisplacement of the displacement part 53 in a direction along the normalline N and not depending on the displacement in a direction orthogonalto the normal line N. This is important in accurately detecting exertedtorque on the basis of the above-described principle.

Consequently, in carrying out the present invention, it is preferablethat one of the fixed electrode E20 and the displacement electrode E50is set to be larger in area than the other so that the pair ofelectrodes which constitute the capacitive element C will not change ineffective opposing area, even where torque in a predetermined rotatingdirection is exerted to cause a change in relative position of thedisplacement electrode E50 in relation to the fixed electrode E20.

In FIG. 24, there is shown the example in which rectangular electrodesare used as two electrodes EL, ES. However, the displacement electrodeE50 and the fixed electrode E20 used in the torque sensor according tothe present invention are given in any shape and, for example, these maybe formed into circular electrodes. Further, as described in Section4-3, it is acceptable that the annular deformation body 50 isconstituted of a conductive material such as a metal and a certaindomain of the surface thereof is used as the displacement electrode E50or the right side support body 20 is constituted of a conductivematerial such as a metal and a certain domain of the surface thereof isused as the fixed electrode E20.

<5-2. Removal of Errors Resulting from Interference with the Other AxisComponents>

In the above-described Section 5-1, the behavior of each of thedetection parts D1 to D4 is described on the assumption that moment Mzaround the Z axis is exerted on the torque sensor according to the basicembodiment of the present invention, thereby showing that computation isperformed on the basis of the arithmetic expression of “Mz=−C1+C2−C3+C4”shown at the bottom line in FIG. 22, thus making it possible to detectexerted moment Mz around the Z axis as torque to be detected.

However, an external force exerted on the torque sensor is notnecessarily limited only to moment Mz around the Z axis. For example, inthe torque sensor shown in FIG. 16, an external force exerted on theleft side support body 10 in a state that the right side support body 20is fixed includes six axis components such as force Fx in the directionof the X axis, force Fy in the direction of the Y axis, force Fz in thedirection of the Z axis, moment Mx around the X axis, moment My aroundthe Y axis and moment Mz around the Z axis. The sensor according to thepresent invention is a sensor which is to detect moment Mz around the Zaxis, among these six axis components, as torque. And, the principle ofdetecting the torque has been already described in Section 5-1.

As a matter of course, depending on use environments of the torquesensor, there is a case where the sensor is used in a state that onlymoment Mz around the Z axis is exerted. For example, where the torquesensor shown in FIG. 16 is used by being housed in a cylindrical tube,with the Z axis given as the central axis, and an external diameter ofthe torque sensor is in agreement with an inner diameter of thecylindrical tube, the left side support body 10 is extremely restrictedin its degree of freedom of movement. In the above-described useenvironment, there is found no problem even when only moment Mz aroundthe Z axis is exerted on the left side support body 10. However, wherethe torque sensor shown in FIG. 16 is incorporated into a joint part ofa robot arm and used as a part of the joint, the above-described sixaxis (force) components are all exerted on the left side support body10.

The torque sensor according to the basic embodiment which has beendescribed above is characterized by being able to detect accurate torquefrom which there is removed interference with the other axis components(among the six axis components, five axis components except for momentMz around the Z axis). Here, a description will be given of a point thatthe interference with the other axis components can be removed accordingto the detection method described in Section 5-1.

FIG. 25 is a table which shows an example covering a specificdisplacement amount of electrode distance of each of the capacitiveelements C1 to C4 when force Fx, Fy, Fz in the direction of each axis ormoment Mx, My, Mz around each axis are exerted on the left side supportbody 10 in a state that the right side support body 20 is fixed at thebasic structural part shown in FIG. 16. FIG. 26 is a table which showsan amount of fluctuation (an extent of increase or decrease) incapacitance value of each of the capacitive elements shown in FIG. 25.In both of the tables, the fields of Mz are enclosed by the thick linedframe, which indicates that a force component which is to be primarilydetected by the torque sensor is moment Mz (torque around the Z axis).

When the row of Mz in the table in FIG. 25 is viewed, “+10” is filled ina field of each of the capacitive elements C1, C3, and “−10” is filledin a field of each of the capacitive elements C2, C4. This indicatesthat when moment +Mz which is positive rotation around the Z axis isexerted on the left side support body 10 in a state that the right sidesupport body 20 is fixed, an electrode distance of each of thecapacitive elements C1, C3 is increased by 10 μm, while an electrodedistance of each of the capacitive elements C2, C4 is decreased by 10 μm(“+” in the table of FIG. 25 indicates an increase in electrode distanceand “−” indicates a decrease in electrode distance). A reason for havingthe above phenomenon is as already described by referring to FIG. 21.

Numerical values indicated in individual fields of the table in FIG. 25are results in which a displacement amount (unit: μm) of electrodedistance of each of the capacitive elements C1 to C4 is actuallymeasured in a specific sample prepared by using a basic structural partdesigned with specific dimensions and constituted of a specificmaterial, when force in the direction of each axis and moment aroundeach axis which have a predetermined reference value are exerted on theleft side support body 10 in a state that the right side support body 20is fixed (in the case of moment, when the force having the referencevalue is exerted on an exertion point away from the origin O by apredetermined reference distance). Therefore, the numerical value ofeach field is a characteristic value obtained from the sample and anabsolute value of each numerical value has no universal meaning.However, the reference symbol thereof indicates an increase or adecrease in electrode distance and has universality, irrespective ofdimensions or materials of the sample to be detected.

When the row of Fx in table of FIG. 25 is viewed, “−2” is filled in thefield of each of the capacitive elements C1, C4, and “+2” is filled inthe field of each of the capacitive elements C2, C3. This indicates thatwhere force +Fx in the positive direction of the X axis is exerted onthe left side support body 10 in a state that the right side supportbody 20 is fixed, the capacitive elements C1, C4 are decreased inelectrode distance by 2 μm, while the capacitive elements C2, C3 areincreased in electrode distance by 2 μm. A reason for developing theabove phenomenon can be easily understood by referring to thedeformation mode in FIG. 27.

FIG. 27 is a sectional view on the XY plane which shows a deformationstate when force +Fx in the positive direction of the X axis is exerted,corresponding to a sectional view in which the basic structural partshown in FIG. 15 is cut along the XY plane and viewed from the rightside in FIG. 15. When force +Fx in the positive direction of the X axisis exerted on the left side connection points P11, P12 indicated by thewhite dot in a state that the right side connection points P21, P22indicated by the black dot are fixed, as shown by the outlined arrow inthe drawing, the left side connection points P11, P12 indicated by thewhite dot move in the rightward direction in the drawing. As a result,the compressive force f1 indicated by the outlined arrow in the drawingis exerted in the vicinities of positions of the first detection pointQ1 and the fourth detection point Q4, and the extension force f2indicated by the outlined arrow in the drawing is exerted in thevicinities of positions of the second detection point Q2 and the thirddetection point Q3.

Consequently, as shown in FIG. 27, the annular deformation body 50 isdeformed into an irregular shape (the broken line in the drawingindicates a state before deformation). Thus, the capacitive elements C1,C4 are decreased in electrode distance by 2 μm, while the capacitiveelements C2, C3 are increased in electrode distance by 2 μm, and thereis obtained the result shown in the row of Fx in the table of FIG. 25.Due to the same reason, when force +Fy in the positive direction of theY axis is exerted, there is obtained the result shown in the row of Fyin the table of FIG. 25. And, the capacitive elements C1, C2 aredecreased in electrode distance by 2 μm, while the capacitive elementsC3, C4 are increased in electrode distance by 2 μm. Further, when force+Fz in the positive direction of the Z axis is exerted, the annulardeformation body 50 undergoes displacement as a whole in the positivedirection of the Z axis, and there is obtained the result shown in therow of Fz in the table of FIG. 25. That is, the capacitive elements C1to C4 are both decreased in electrode distance by 5 μm.

On the other hand, FIG. 28 is a side view which shows a deformationstate when moment +Mx which is positive rotation around the X axis isexerted. In the drawing, the X axis is an axis which passes through theorigin O and is orthogonal to the sheet surface, and moment +Mx which ispositive rotation around the X axis is force which rotates clockwise theleft side support body 10 in the drawing. As a result, the firstdetection part D1 (not visible in the drawing) and the second detectionpart D2 which are disposed above from the XZ plane undergo displacementso as to move close to the right side support body 20. The thirddetection part D3 and the fourth detection part D4 (not visible in thedrawing) which are disposed below from the XZ plane undergo displacementso as to move away from the right side support body 20.

Thus, there is obtained the result shown in the row of Mx in the tableof FIG. 25. The capacitive elements C1, C2 are decreased in electrodedistance by 100 μm, while the capacitive elements C3, C4 are increasedin electrode distance by 100 μm. Due to the same reason, when moment +Mywhich is positive rotation around the Y axis is exerted, there isobtained the result shown in the row of My in the table of FIG. 25. Thecapacitive elements C1, C4 are increased in electrode distance by 60 μm,while the capacitive elements C2, C3 are decreased in electrode distanceby 60 μm. An absolute value of increase/decrease in electrode distanceupon exertion of moment +Mx is 100 μm, while an absolute value ofincrease/decrease in electrode distance upon exertion of moment +My is60 μm. This is because, as shown in FIG. 15, the protruding parts 21, 22(right side connection members) are disposed at positions along the Xaxis, by which displacement around the X axis occurs more easily thandisplacement around the Y axis.

As described above, FIG. 26 is a table which shows an amount offluctuation (an extent of increase or decrease) in capacitance value ofeach of the capacitive elements prepared on the basis of the table shownin FIG. 25. And, “+” of each field indicates an increase in capacitancevalue, while “−” indicates a decrease in capacitance value. Since anincrease/decrease in electrode distance is reversed to that incapacitance value, reference symbols of individual fields in the tableof FIG. 26 are reverse in relationship to reference symbols ofcorresponding fields in the table of FIG. 25.

Further, in the table of FIG. 26, in order to indicate not only areference symbol but also an approximate absolute value, three differentreference symbols such as “(+),” “+” and “++” are used in the case of anincrease in capacitance value, and three different reference symbolssuch as “(−),” “−” and “−−” are used in the case of a decrease incapacitance value. Here, “(+)” and “(−)” indicate that an absolute valueof the numerical value shown in the table of FIG. 25 is less than 5, “+”and “−” indicate that an absolute value thereof is 5 or more but lessthan 50, and “++” and “−−” indicate that an absolute value thereof is 50or more. As apparent from the table of FIG. 25, an absolute value ofnumerical value of each field belonging to the same row is equal to eachother. Where the row is different, an absolute value of numerical valueis also different (however, as for the rows Fx, Fy, absolute values ofnumerical values are all the same “2”).

As already described in Section 5-1, in the torque sensor according tothe basic embodiment described here, a computation value of Mz obtainedon the basis of the arithmetic expression “Mz=−C1+C2−C3+C4” is output asa value of torque to be detected. Therefore, in actuality, the detectioncircuit shown in FIG. 23 is used to output a detection value at theoutput terminal T. With reference to the row of Mz in the table of FIG.26, it will be understood that the computation value Mz obtained on thebasis of the arithmetic expression “Mz=−C1+C2−C3+C4” is a value whichindicates correct torque (moment Mz around the Z axis).

For example, for the sake of convenience, when an absolute value of anamount of fluctuation indicated by “−” or “+” is assumed to be “a” andC1=−a, C2=+a, C3=−a and C4=+a are given depending on the row of Mz, bywhich a computation result of the above arithmetic expression is to beMz=+4a. This indicates that there is exerted torque which is positiverotation around the Z axis and corresponds to an absolute value of 4a.As a matter of course, where there is exerted torque which is reverserotation, reference symbols in the row of Mz are reversed, and acomputation result of the above arithmetic expression is Mz=−4a. Thisindicates that there is exerted torque which is negative rotation aroundthe Z axis and corresponds to an absolute value of 4a. As describedabove, upon exertion of moment Mz around the Z axis, it is possible todetect without any difficulty the direction (reference symbol) andmagnitude (absolute value) of moment Mz as a computation value by theabove-described arithmetic expression.

Next, consideration is given to a case where forces of other axiscomponents except for moment Mz are exerted on the left side supportbody 10. At first, where force Fx in the direction of the X axis isexerted, an amount of fluctuation in each of the capacitance values C1to C4 is given in the row of Fx in FIG. 26. Also here, for the sake ofconvenience, when an absolute value of an amount of fluctuationindicated by “(+)” or “(−)” is assumed to be “a” and C1=+a, C2=−a, C3=−aand C4=+a are given depending on the row of Fx, by which a computationresult of the above-described arithmetic expression is to be Mz=0. Thisindicates that the computation result of the arithmetic expression willnot include a component of force Fx.

Similarly, where force Fy in the direction of the Y axis is exerted, anamount of fluctuation in each of the capacitance values C1 to C4 isgiven by the row of Fy in FIG. 26. Also here, for the sake ofconvenience, when an absolute value of an amount of fluctuationindicated by “(+)” or “(−)” is assumed to be “a” and C1=+a, C2=+a, C3=−aand C4=−a are given depending on the row of Fy, by which a computationresult of the above arithmetic expression is to be Mz=0. This indicatesthat the computation result of the arithmetic expression will notinclude a component of force Fy.

Further, where force Fz in the direction of the Z axis is exerted, anamount of fluctuation in each of the capacitance values C1 to C4 isgiven by the row of Fz in FIG. 26. Also here, for the sake ofconvenience, an absolute value of an amount of fluctuation indicated by“+” is assumed to be “a” and C1=+a, C2=+a, C3=+a and C4=+a are givendepending on the row of Fz, by which a computation result of theabove-described arithmetic expression is to be Mz=0. This indicates thatthe computation result of the arithmetic expression will not include acomponent of force Fz.

Further, where moment Mx around the X axis is exerted, an amount offluctuation in each of the capacitance values C1 to C4 is given in therow of Mx in FIG. 26. Also here, for the sake of convenience, anabsolute value of an amount of fluctuation indicated by “++” and “−−” isassumed to be “a” and C1=+a, C2=+a, C3=−a and C4=−a are given dependingon the row of Mx, by which a computation result of the above-describedarithmetic expression is to be Mz=0. This means that the computationresult of the arithmetic expression will not include a component ofmoment Mx.

Lastly, where moment My around the Y axis is exerted, an amount offluctuation in each of the capacitance values C1 to C4 is given in therow of My in FIG. 26. Also here, for the sake of convenience, anabsolute value of the amount of fluctuation indicated by “++” or “−−” isassumed to be “a” and C1=−a, C2=+a, C3=+a, and C4=−a are given dependingon the row of My, by which a computation result of the above-describedarithmetic expression is to be Mz=0. This indicates that the computationresult of the arithmetic expression will not include a component ofmoment My.

Consequently, the computation value Mz obtained by the arithmeticexpression of “Mz=−C1+C2−C3+C4” will not include at all other axiscomponents Fx, Fy, Fz, Mx, My, and the computation value concerned is avalue which indicates only a component of moment Mz around the Z axis.As described above, the torque sensor shown in FIG. 16 removesinterference with the other axis components Fx, Fy, Fz, Mx, My evenwhere it is used as a part of a joint of a robot arm, etc., and able todetect correct torque which indicates only a component of moment Mz.

<<Section 6. Characteristics of Basic Embodiment of the PresentInvention>>

In Section 4 and Section 5, a description has been given of theconstitution and motions of the torque sensor according to the basicembodiment of the present invention which uses the basic structural partshown in FIG. 15. Here, characteristics of the torque sensor accordingto the basic embodiment will be summarized.

The torque sensor according to the present invention is a sensor whichdetects torque around a predetermined rotation axis, and the basicstructural part is provided with the left side support body 10, theannular deformation body 50 and the right side support body 20 as shownin FIG. 15. Here, as shown in FIG. 15, when an XYZ three-dimensionalcoordinate system is defined, and the Z axis is given as a rotationaxis, the XY plane orthogonal to the rotation axis is given as a basicplane, a basic annular channel R is defined on the basic plane XY so asto surround a circumference of the rotation axis Z, the annulardeformation body 50 has an annular structure extending along the basicannular channel R (refer to FIG. 18).

Here, when the basic structural part is viewed, as shown in FIG. 15, inthe reference observation direction in which the rotation axis Z gives ahorizontal line extending laterally, the left side support body 10 isdisposed at a position adjacent to the left side of the annulardeformation body 50 and the right side support body 20 is disposed at aposition adjacent to the right side of the annular deformation body 50.Then, when the left side connection points P11, P12 are defined at thepositions indicated by the white dot in FIG. 18 on the left side surfaceof the annular deformation body 50 and the right side connection pointsP21, P22 indicated by the black dot in FIG. 18 are defined on the rightside surface of the annular deformation body 50, the left side surfaceof the annular deformation body 50 is connected to the left side supportbody 10 at positions of the left side connection points P11, P12 by theleft side connection members 11, 12. And, the right side surface of theannular deformation body 50 is connected to the right side support body20 at positions of the right side connection points P21, P22 by theright side connection members 21, 22.

The torque sensor according to the basic embodiment described in Section4 and Section 5 is constituted by adding a capacitive element C and adetection circuit to the basic structural part. Here, as shown in FIG.20, the capacitive element Cis constituted of a displacement electrodeE50 fixed at a predetermined position on the right side surface of theannular deformation body 50 and a fixed electrode E20 fixed at aposition of the right side support body 20 which opposes thedisplacement electrode E50. Next, on the basis of fluctuation incapacitance value of each of the capacitive elements, the detectioncircuit has functions to output, in a state that a load is applied toone of the left side support body 10 and of the right side support body20, an electric signal indicating torque around the rotation axis Zwhich is exerted on the other.

As shown in FIG. 18, the detection points Q1 to Q4 are defined on thebasic annular channel Ron the annular deformation body 50, and thedetection parts D1 to D4 are disposed at the positions of the detectionpoints Q1 to Q4. Next, as shown in FIG. 15, the annular deformation body50 is structured so that the detection parts D1 to D4 and the couplingparts L1 to L4 are alternately disposed. To both ends of each of thedetection parts D, the coupling part L adjacent to each of them isconnected. Further, as shown in FIG. 18, the left side connection pointsP11, P12 and the right side connection points P21, P22 are individuallydisposed on the coupling parts L. And, orthogonal projection images(white dots) of the left side connection points P11, P12 and orthogonalprojection images (black dots) of the right side connection points P21,P22 on the basic plane XY are formed at mutually different positions.Therefore, a compressive force f1 or an extension force f2 is exerted oneach of the detection parts D1 to D4, depending on exertion of torque.

As shown in FIG. 20, each of the detection parts D is provided with afirst deformation part 51 and a second deformation part 52 for causingelastic deformation by exertion of torque to be detected and adisplacement part 53 for undergoing displacement resulting from elasticdeformation of these deformation parts 51, 52. Next, an external end ofthe first deformation part 51 is connected to a coupling part L adjacentthereto and an internal end thereof is connected to the displacementpart 53. Similarly, an external end of the second deformation part 52 isconnected to a coupling part L adjacent thereto and an internal endthereof is connected to the displacement part 53. Next, the displacementelectrode E50 is fixed at a position of the displacement part 53 whichopposes the right side support body 20.

As shown in FIG. 18, in the case of the torque sensor according to thebasic embodiment of the present invention, the left side connectionpoints P11, P12 are provided at two sites and the right side connectionpoints P21, P22 are also provided at two sites. In other words, theannular deformation body 50 is connected to the left side support body10 at the two sites and also connected to the right side support body 20at the two sites. Of course, according to the principle of the presentinvention, it will be sufficient that the annular deformation body 50 isconnected to the left side support body 10 at least at one site and theannular deformation body 50 is also connected to the right side supportbody 20 at least at one site. Therefore, the left side connection pointand the right side connection point are not necessarily provided at twosites each. However, in practice, it is preferable that the left sideconnection point and the right side connection point are provided atleast at two sites each in order to stably transmit exerted torque tothe annular deformation body 50.

Further, in the case of the torque sensor according to the basicembodiment of the present invention, the detection points Q1 to Q4 aredefined at four sites on the annular deformation body 50 and the foursets of detection parts D1 to D4 are provided in total. However,according to the principle of the present invention, only one set of thedetection part D is able to detect torque. For example, in the case ofthe detection part D shown in FIG. 20, when a compressive force f1(force which allows the detection part D to contract vertically in thedrawing) is exerted in the vicinity of the detection point Q, thecapacitive element C is increased in capacitance value. When anextension force f2 (force which allows the detection part D to expandvertically in the drawing) is exerted, the capacitive element C isdecreased in capacitance value. Therefore, an increase or a decreasethereof depends on the magnitude of exerted force. As a result, inprinciple, one set of the detection part D is provided at a part of theannular deformation body 50, thus making it possible to detect thedirection and magnitude of exerted torque on the basis of a change incapacitance value of the capacitive element C.

However, in practice, it is preferable that n number (n≥2) of aplurality of detection points are defined on the basic annular channel Rand the detection parts D are disposed at the individual detectionpoints. In other words, it is preferable that the annular deformationbody 50 is constituted by alternately disposing n-number of theplurality of detection parts D and n-number of the plurality of couplingparts L along the basic annular channel R. This is because n-number ofthe plurality of detection parts D are disposed, by which detection canbe performed by using capacitance values of n-number of the plurality ofcapacitive elements C to further enhance the detection accuracy.

Furthermore, on the basis of a displacement mode of the displacementpart 53 (upon exertion of torque in a specific direction, it moves closeto or moves away from the right side support body 20), n-number of theplurality of detection parts are divided into two types of attributegroups, by which detection can be made on the basis of a difference incapacitance value to provide such an effect that further enhances thedetection accuracy.

In practice, it is preferable that n is set to be an even number, n-evennumber (n≥2) of detection points are defined on the basic annularchannel R and the detection parts D are disposed at the individualdetection points. In other words, it is preferable that the annulardeformation body 50 is constituted by alternately disposing n evennumber of the detection parts D and n even number of the coupling partsL along the basic annular channel R. Thereby, when n number of thedetection parts are divided into two types of attribute groups, thesecan be divided into a group each composed of the same number of groupsto perform stable detection which is free of bias.

Further, when n is set to be an even number and n even number ofcoupling parts L are numbered sequentially along the basic annularchannel R, the right side connection point can be disposed at anodd-numbered coupling part and the left side connection point can bedisposed at an even-numbered coupling part. Therefore, torque exerted onthe left side support body 10 can be efficiently transmitted to theannular deformation body 50 to make stable deformation of the annulardeformation body 50. The torque sensor according to the basic embodimentdescribed in Section 4 and Section 5 is an example in which n is set tobe equal to 4.

As a matter of course, n is set to be equal to 2 and the two sets ofdetection parts D are provided on the annular deformation body 50, thusmaking it possible to obtain the above-described effect of enhancing thedetection accuracy. That is, where n is set to be equal to 2, it will besufficient that the annular deformation body is constituted by disposingindividual parts in the order of the first coupling part, the firstdetection part, the second coupling part and the second detection partalong the basic annular channel R, and the right side connection pointis disposed at the first coupling part and the left side connectionpoint is disposed at the second coupling part.

However, in practice, it is preferable that n is set to be 4 or more ofan even number, and the basic embodiment described in Section 4 andSection 5 is one of the most preferable embodiments. Where n is set tobe equal to 4, as shown in FIG. 17, the annular deformation body 50 isconstituted by disposing individual parts in the order of a firstcoupling part L1, a first detection part D1, a second coupling part L2,a second detection part D2, a third coupling part L3, a third detectionpart D3, a fourth coupling part L4 and a fourth detection part D4 alongthe basic annular channel R.

In addition, as apparent with reference to FIG. 17 and FIG. 18, thefirst right side connection point P21 is disposed at the first couplingpart L1, the first left side connection point P11 is disposed at thesecond coupling part L2, the second right side connection point P22 isdisposed at the third coupling part L3, and the second left sideconnection point P12 is disposed at the fourth coupling part L4.Therefore, as shown in FIG. 15, the left side connection member isconstituted of a first left side connection member 11 which connects thefirst left side connection point P11 with the left side support body 10and a second left side connection member 12 which connects the secondleft side connection point P12 with the left side support body 10. And,the right side connection member is constituted of a first right sideconnection member 21 which connects the first right side connectionpoint P21 with the right side support body 20 and a second right sideconnection member 22 which connects the second right side connectionpoint P22 with the right side support body 20.

Therefore, when torque around the Z axis is exerted on the left sidesupport body 10 in a state that the right side support body 20 is fixed,the torque is reliably transmitted by the first left side connectionmember 11 and the second left side connection member 12 to the secondcoupling part L2 and the fourth coupling part L4. On the other hand, thefirst coupling part L1 and the third coupling part L3 are firmly keptfixed to the right side support body 20 by the first right sideconnection member 21 and the second right side connection member 22.Thus, stable deformation occurs on the annular deformation body 50 onthe basis of exerted torque.

Further, in the torque sensor according to the basic embodiment, each ofthe connection points is disposed so as to give symmetry to the centralaxis. Specifically, as shown in FIG. 18, where two straight lines (Xaxis and Y axis) are drawn so as to pass through an intersection Obetween the basic plane (XY plane) and the rotation axis Z and areorthogonal to each other, orthogonal projection images (white dots) ofthe first left side connection point P11 and the second left sideconnection point P12 are disposed on a first straight line (on the Yaxis). And, orthogonal projection images (black dots) of the first rightside connection point P21 and the second right side connection point P22are disposed on a second straight line (on the X axis).

That is, where the XYZ three-dimensional coordinate system shown in thedrawing is defined, the annular deformation body 50 is disposed on theXY plane which is a basic plane, with the origin O given as the center,the left side support body 10 is disposed at a negative domain of the Zaxis (a position behind the sheet surface), and the right side supportbody 20 is disposed at a positive domain of the Z axis (a positionforward from the sheet surface). Next, the first left side connectionpoint P11 and the second left side connection point P12 are provided onthe side surface of the annular deformation body 50 on the negative sideof the Z axis. The first right side connection point P21 and the secondright side connection point P22 are provided on the side surface of theannular deformation body 50 on the positive side of the Z axis.

Here, where both of the side surfaces of the annular deformation body 50are projected on the XY plane to obtain orthogonal projection images, aprojection image (black dot) of the first right side connection pointP21 is disposed on the positive X axis, a projection image (black dot)of the second right side connection point P22 is disposed on thenegative X axis, a projection image (white dot) of the first left sideconnection point P11 is disposed on the positive Y axis, and aprojection image (white dot) of the second left side connection pointP12 is disposed on the negative Y axis. As described above, two upperand lower sites of the annular deformation body 50 are joined to theleft side support body 10, and two left and right sites thereof arejoined to the right side support body 20, by which each of theconnection points deviates by every 90 degrees. Thereby, the annulardeformation body 50 can be deformed efficiently by exertion of torqueand also deformed into an elliptical shape having axial symmetry. Theaxial symmetry is favorable in performing the difference detection onthe basis of capacitance values.

On the other hand, as shown in FIG. 18, where the V axis is defined as acoordinate axis in which the X axis is rotated counterclockwise by 45degrees on the XY plane, with the origin O given as the center, and theW axis is defined as a coordinate axis in which the Y axis is rotatedcounterclockwise by 45 degrees, with the origin O given as the center,the first detection point Q1 is disposed on the positive V axis, thesecond detection point Q2 is disposed on the positive W axis, the thirddetection point Q3 is disposed on the negative V axis, and the fourthdetection point Q4 is disposed on the negative W axis. Next, four setsof the detection parts D1 to D4 are disposed so that each of thedetection points Q1 to Q4 is given as the center, giving symmetry withrespect to the V axis and the W axis.

If the above-described constitution is adopted, a total of four sets ofthe capacitive elements C1 to C4 are disposed on both positive andnegative sides of the V axis and the W axis. Thus, upon exertion of aspecific torque, difference detection can be performed by using two setsof capacitive elements with an increase in capacitance value and twosets of capacitive elements with a decrease in capacitance value toenhance the detection accuracy. In the case of the basic embodiment,four sets of the detection parts D1 to D4 are identical in size andstructure to each other and four sets of the capacitive elements C1 toC4 are also identical in size and structure to each other. Therefore,the basic embodiment is a suitable sensor to perform the differencedetection on the basis of capacitance values.

In general, in order to perform difference detection on the basis ofcapacitance values in a torque sensor having n number of a plurality ofdetection parts D, among n number of the detection parts D, some of themmay be detection parts having the first attribute and the others may bedetection parts having the second attribute.

Here, the attribute of the detection part D is determined on the basisof a displacement mode of the displacement part 53 (whether the partmoves close to or moves away from the right side support body 20 uponexertion of torque in a particular direction). That is, a firstattribute displacement part 53 which constitutes a first attributedetection part undergoes displacement in a direction moving away fromthe right side support body 20 upon exertion of torque at a firstrotating direction (for example, moment +Mz) and undergoes displacementin a direction moving close to the right side support body 20 uponexertion of torque in a second rotating direction which is reverse tothe first rotating direction (for example, moment −Mz). In contrast, asecond attribute displacement part 53 which constitutes a secondattribute detection part undergoes displacement in a direction movingclose to the right side support body 20 upon exertion of torque in thefirst rotating direction (moment +Mz) and undergoes displacement in adirection moving away from the right side support body 20 upon exertionof torque in the second rotating direction (moment −Mz).

Next, the first attribute capacitive element is constituted of a firstattribute displacement electrode fixed at the first attributedisplacement part and a first attribute fixed electrode fixed at aposition of the right side support body 20 which opposes the firstattribute displacement electrode. The second attribute capacitiveelement is constituted of a second attribute displacement electrodefixed at the second attribute displacement part and a second attributefixed electrode fixed at a position of the right side support body 20which opposes the second attribute displacement electrode. Thereby, thedetection circuit is able to output an electric signal corresponding toa difference between a capacitance value of the first attributecapacitive element and a capacitance value of the second attributecapacitive element as an electric signal which indicates exerted torque.

In the case of the example shown in the table of FIG. 22, the detectionparts D1, D3 serve as the first attribute detection parts, while thedetection parts D2, D4 serve as the second attribute detection parts.The first attribute capacitive elements C1, C3 are constitutedrespectively with first attribute displacement electrodes E501, E503 andfirst attribute fixed electrodes E201, E203. And, the second attributecapacitive elements C2, C4 are constituted respectively with secondattribute displacement electrodes E502, E504 and second attribute fixedelectrodes E202, E204. As shown in the drawing, upon exertion of torque+Mz, the first attribute capacitive elements C1, C3 are decreased incapacitance value, while the second attribute capacitive elements C2, C4are increased in capacitance value. Therefore, on the basis of thearithmetic expression “Mz=−C1+C2−C3+C4,” a difference between a sum of“C1+C3” of capacitance values C1, C3 of the first attribute capacitiveelements C1, C3 and a sum of “C2+C4” of capacitance values C2, C4 of thesecond attribute capacitive elements C2, C4 is determined, thus makingit possible to detect the direction and magnitude of exerted torque.

Further, as described in Section 5-2, difference detection on the basisof the arithmetic expression “Mz=−C1+C2−C3+C4” can be performed toremove interference with the other axis components. Therefore, where thetorque sensor is used as a part of a joint of a robot arm, other axiscomponents such as Fx, Fy, Fz, Mx, My can be removed to detectaccurately only torque to be detected around the Z axis (moment Mz).

<<<Section 7. Modification Example of Torque Sensor According to thePresent Invention>>>

In Section 4 to Section 6, a description has been given above of thetorque sensor according to the basic embodiment of the presentinvention. Here, there will be described some modification examples ofthe basic embodiment.

<7-1. Modification Example to which Auxiliary Connection Members areAdded>

As described above, the torque sensor according to the basic embodimentis provided with functions to remove interference with the other axiscomponents. That is, where six axis components of Fx, Fy, Fz, Mx, My, Mzare applied to the left side support body 10 in a state that the rightside support body 20 is fixed, an amount of fluctuation in capacitancevalue of each of four sets of the capacitive elements C1 to C4 will beas shown in the table of FIG. 26. Therefore, as described in Section5-2, a value of Mz obtained by computation on the basis of thearithmetic expression of “Mz=−C1+C2−C3+C4” includes only a component ofmoment Mz and is able to remove interference with the other axiscomponents.

This is because the torque sensor has axial symmetry and, with theresults of the table of FIG. 26 taken into account, even where the otherfive axis components of Fx, Fy, Fz, Mx, My are exerted, the computationresults of the basis of the above-described arithmetic expression are tobe zero. In the table of FIG. 26, there are described reference symbolssuch as (+), +, ++, (−), −, −−, depending on the magnitude of absolutevalue of the amount of fluctuation. Where the basic structural part hasaxial symmetry, as shown in the table of FIG. 25, absolute values ofnumerical values of the same row in the table are equal to each other.The computation results of the other five axis components are also allto be zero.

As described above, theoretically, the torque sensor according to thebasic embodiment is able to remove interference with the other axiscomponents and detect accurately only moment Mz around the Z axis.However, in actuality, it is difficult to make completely equal theabsolute values of numerical values of the same row in the table of FIG.25, with some errors found. In other words, in actual products, it isimpossible to obtain a detection value from which interference with theother five axis components is completely removed. As a matter of course,where interference with the other axis components is such an extent thatcan be disregarded as an error, there will be found no practicalproblems. The modification example which will be described here is adevice inventively prepared for reducing further errors resulting frominterference with the other axis components.

In the table of FIG. 26, the original component to be detected is momentMz indicated by being enclosed by a thick lined frame. However,reference symbols of the fields of Mz are + and −, while referencesymbols of the fields of Mx, My which are other axis components are ++and −−. In terms of an absolute value, the other axis components Mx, Myare greater in the amount of fluctuation than the original component ofMz. Specifically, in the case of the example shown in FIG. 25, anabsolute value of an amount of fluctuation is “10” for Mz, whileabsolute values of amounts of fluctuation are respectively “100” and“60” for Mx and My.

As a matter of course, the results shown in FIG. 25 cover valuesobtained from the particular sample designed with specific dimensionsand, therefore, values thereof do not have a specific significance. In atorque sensor which uses a basic structural part having the mode shownin FIG. 15, there is found such a general tendency that components Mx,My, are greater in an amount of fluctuation than a component Mz. This isbecause the basic structural part concerned is characterized by beingmore easily rotated around the X axis or the Y axis than around the Zaxis. Therefore, it can be said that the other axis components Mx, Myare components which will easily influence a detection value of thecomponent Mz which is an original detection target.

FIG. 29 and FIG. 30 are respectively an exploded perspective view and aside view, each of which shows a basic structural part of a torquesensor according to the modification example in which an error resultingfrom interference with the other axis components is reduced further inan inventive manner, with the above problems taken into account. Thebasic structure part of this torque sensor is different from the basicstructural part of the torque sensor according to the basic embodimentshown in FIG. 15 only in that auxiliary connection members 23, 24 areadded. In FIG. 29, the auxiliary connection members 23, 24 are eachshown as a member protruding to the left side from the left side surfaceof the right side support body 20. In actuality, as shown in the sideview of FIG. 30, the auxiliary connection members 23, 24 may be providedin any mode as long as these are members which connect the right sidesurface of the annular deformation body 50 with the left side surface ofthe right side support body 20.

FIG. 31 is a front view which shows a state in which the auxiliaryconnection members 23, 24 are joined to the annular deformation body 50shown in FIG. 29, when viewed from the right side in FIG. 29. In thecase of the example shown in the drawing, the auxiliary connectionmembers 23, 24 are cylindrical members, and projection images thereof onthe XY plane are positioned on the Y axis. As shown by the white dot inFIG. 18, left side connection points P11, P12 are defined on the Y axis,and the auxiliary connection members 23, 24 are connected to positionsof the left side connection points P11, P12. In other words, on the XYplane, the auxiliary connection member 23 is disposed at a connectionposition of a first left side connection member 11 (indicated by thebroken line in FIG. 31) and the auxiliary connection member 24 isdisposed at a connection position of a second left side connectionmember 12 (indicated by the broken line in FIG. 31).

FIG. 32 is a partial sectional view which shows a structure in thevicinity of the auxiliary connection member 23 at the basic structuralpart shown in FIG. 29, and the white dot indicates the left sideconnection point P11. That is, FIG. 32 corresponds to a sectional viewin which the basic structural part is cut along a plane which includesthe left side connection point P11 and is parallel to the XZ plane (thevertical direction in the drawing is the direction of the Z axis). Aconnection reference line A indicated by the broken line in the drawingis a straight line which passes through the left side connection pointP11 and is parallel to the Z axis. The auxiliary connection member 23 isa cylindrical member, with the connection reference line A given as thecentral axis. It functions as what-is-called “a supporting rod” forkeeping constant a clearance between the annular deformation body 50(coupling part L2) and the right side support body 20 at the position ofthe connection reference line A. The auxiliary connection member 24 alsoperforms the same function.

As apparent from the side view of FIG. 30, the auxiliary connectionmembers 23, 24, each of which functions as “a supporting rod,” areadded, by which even when moment Mx around the X axis is exerted on theleft side support body 10 in a state that the right side support body 20is fixed, the left side support body 10 and the annular deformation body50 are suppressed for displacement. That is, there occurs nodisplacement as shown in FIG. 28, even upon exertion of moment Mx.Further, the auxiliary connection members 23, 24 are added to obtain aneffect which suppresses displacement occurring upon exertion of momentMy. This is because the auxiliary connection members 23, 24 function asresistance factors to rotational movement around the Y axis.

In the example shown here, there are used cylindrical members disposedon the connection reference line A, as the auxiliary connection members23, 24. As a matter of course, the shape of the auxiliary connectionmembers 23, 24 shall not be restricted to a cylindrical shape.Furthermore, the auxiliary connection members 23, 24 are not necessarilypositioned on the connection reference line A and may be disposed at aposition slightly away from the connection reference line A, as long asthey are in the vicinity thereof. For instance, in the example shown inFIG. 31, the position of the auxiliary connection member 23 is allowedto move in the positive direction of the Y axis and the position of theauxiliary connection member 24 is allowed to move in the negativedirection of the Y axis, by which both of them may be disposed in thevicinity of an external contour line of the annular deformation body 50.Alternatively, as indicated by the broken line in the drawing, a raisedpart L2 a formed by expanding the coupling part L2 outward and a raisedpart L4 a formed by expanding the coupling part L4 outward may beprovided at an intersecting part with the Y axis of the annulardeformation body 50, the auxiliary connection member 23 may be disposedat a position of the raised part L2 a indicated by the triangle mark andthe auxiliary connection member 24 may be disposed at a position of theraised part L4 a indicated by the triangle mark. In this case, similarraised parts may also be provided at positions which oppose the raisedparts L2 a, L4 a in the right side support body 20.

In other words, the auxiliary connection members 23, 24 are memberswhich are provided between the right side surfaces of the coupling partsL2, L4 (including the raised parts formed by expansion thereof) of theannular deformation body 50 and an opposing surface of the right sidesupport body 20 (including the raised part formed by expansion thereof),and when a connection reference line parallel to the rotation axis (Zaxis) passes through the left side connection points P11, P12 isdefined, any member may be used as the auxiliary connection member aslong as they are disposed on the connection reference line A or thevicinity thereof. It is noted that a certain effect can be obtained evenwhen only one of the auxiliary connection members 23, 24 is provided.However, in practice, it is preferable that both of them are provided.

An object of providing the auxiliary connection members 23, 24 is tosuppress displacement resulting from exertion of moment Mx, My of theother axis components in comparison with displacement resulting fromexertion of moment Mz of the original detection target, thereby furtherreducing errors derived from interference with the other axiscomponents. With this object taken into account, as the auxiliaryconnection members 23, 24, such a member is preferably used that causeselastic deformation more easily upon exertion of force in a directionorthogonal to the connection reference line A than upon exertion offorce in a direction along the connection reference line A.

Specifically, as shown in the example of FIG. 32, an elongated rod-likemember made of a material having certain elasticity, for example, ametal or a resin, may be used as the auxiliary connection member 23 anddisposed along the connection reference line A. Then, elasticdeformation is less likely to occur when force is exerted in thevertical direction in the drawing along the connection reference line Aon the left side support body 10 in a state that the right side supportbody 20 is fixed. However, elastic deformation is more likely to occurwhen force is exerted in the lateral direction in the drawing, that is,in a direction orthogonal to the connection reference line A.

In other words, the auxiliary connection member 23 made of an elongatedrod-like member is less likely to cause deformation contracting orexpanding in the vertical direction but more likely to cause deformationdeclining laterally as a whole. As a result, the annular deformationbody 50 is sufficiently suppressed for displacement in the verticaldirection in the drawing, thereby greatly restricting displacement onthe basis of exertion of moment Mx. However, the auxiliary connectionmember 23 is declined, by which the annular deformation body 50 is notsufficiently suppressed for displacement in the lateral direction in thedrawing, thus resulting in insufficient restriction of displacement onthe basis of exertion of moment Mz. In actuality, the auxiliaryconnection members 23, 24 are provided, thus making it possible tosuppress displacement on the basis of exertion of moment My ordisplacement on the basis of force Fz.

FIG. 33 is a partial sectional view which shows a modification exampleof a structure in the vicinity of the auxiliary connection member shownin FIG. 32. This modification example is modified in an inventive mannerso that the auxiliary connection member 23 can be more easily inclinedand a diaphragm is provided at a part which connects both ends of theauxiliary connection member. A basic structural part according to themodification example is slightly different in shape from the basicstructural part of the basic embodiment described above. Thus, “A” isgiven to an end of a reference symbol which indicates each part in thedrawing. That is, a left side support body 10A is connected to anannular deformation body 50A (coupling part L2) by a left sideconnection member which has a connection member main body 11A and aconnection member base 11P. And, the annular deformation body 50A isconnected to a right side support body 20A by an auxiliary connectionmember 23A.

Here, a connecting part of the annular deformation body 50A with theauxiliary connection member 23A is constituted of a diaphragm part 50 d.And, a connecting part of the right side support body 20A with theauxiliary connection member 23A is constituted of a diaphragm part 20 d.Therefore, when torque around the Z axis is exerted on the left sidesupport body 10A in a state that the right side support body 20A isfixed, the diaphragm parts 50 d, 20 d are deformed by the exertedtorque, by which the auxiliary connection member 23A is inclined to theconnection reference line A. Therefore, despite the fact that theauxiliary connection member 23A is provided, degree of freedom ofdisplacement on the basis of torque to be detected (moment Mz) issufficiently secured.

Since the auxiliary connection member 23 shown in FIG. 32 is required toundergo deformation itself for inclination, it is preferably constitutedof a rod-like member which is as narrow as possible. In contrast, sincethe auxiliary connection member 23A shown in FIG. 33 is inclined due todeformation of the diaphragm parts 50 d, 20 d, the auxiliary connectionmember 23A itself is not required to undergo deformation. Therefore, theauxiliary connection member 23A may be constituted by using a thickrigid member. In order to secure a sufficient inclination angle, theauxiliary connection member is preferably made as long as possible.

Further, in the case of the example shown in the drawing, the left sideconnection member is constituted of a connection member main body 11Aand a connection member base 11P, and the connection member base 11P iskept away from the diaphragm part 50 d but connected to acircumferential part thereof. Thus, the diaphragm part 50 d will not beprevented from undergoing deformation. Accordingly, the auxiliaryconnection member 23A is secured so as to be inclined at a sufficientdegree of freedom. In the case of the example shown in the drawing, sucha constitution is adopted that the diaphragm part 50 d is provided atthe annular deformation body 50A and the diaphragm part 20 d is providedat the right side support body 20A, thereby connecting both upper andlower ends of the auxiliary connection member 23A via the diaphragmparts. There may be adopted a constitution in which only the upper endor the lower end is connected by the diaphragm part.

FIG. 34 is a table which shows an amount of fluctuation (an extent ofincrease or decrease) in capacitance value of each of the capacitiveelements when force in the direction of each axis or moment around eachaxis is exerted on the left side support body 10 of the modificationexample to which the auxiliary connection members shown in FIG. 29 areadded. In comparison with the table shown in FIG. 26, it is found thatany of the fields of Fz, the fields of Mx and the fields of My are (+)or (−). It is noted that specific classification criteria of this tablebetween a numerical value range of an amount of fluctuationcorresponding to the reference symbols of “(+)” and “(−)” and anumerical value range of an amount of fluctuation corresponding to thereference symbols of “+” and “−” are slightly different from theclassification criteria of the table in FIG. 26 (“(+),” “(−)” forabsolute values of less than 5 and “+,” “−” for absolute values of 5 ormore but less than 50). However, it remains unchanged that the referencesymbols of “(+)” and “(−)” indicate much smaller absolute values thanthe reference symbols of “+,” “−.”

As apparent from comparison between the table of FIG. 26 and the tableof FIG. 34, the auxiliary connection members are added, by which anabsolute value of an amount of fluctuation is decreased upon exertion offorce Fz and moment Mx, My. And, an absolute value of an amount offluctuation upon exertion of the other axis components such as Fx, Fy,Fz, Mx and My is relatively decreased, in comparison with an absolutevalue of an amount of fluctuation upon exertion of moment Mz to bedetected. Therefore, it is possible to reduce further errors resultingfrom interference with the other axis components.

<7-2. Modification Example which Uses a Total of Eight Sets of DetectionParts>

In Section 6, it has been described that in carrying out the presentinvention, n number (n≥2) of a plurality of detection points arepreferably defined on the basic annular channel R and the detection partD is disposed at each of the detection points. In the basic embodiment,n is set to be equal to 4 and a total of four sets of the detectionparts are used. In a modification example to be described here, n is setto be equal to eight and a total of eight sets of detection parts areused. Therefore, in the torque sensor according to the modificationexample, in place of the annular deformation body 50 of the basicstructural part shown in FIG. 15, there is used an annular deformationbody 60 which is provided with eight sets of detection parts D11 to D18.

It is noted that the left side support body 10 and the right sidesupport body 20 are unchanged in structure. Therefore, where an XYZthree-dimensional coordinate system is defined, in the case of thetorque sensor according to this modification example as well, theannular deformation body 60 is disposed on the XY plane which is a basicplane, with the origin O given as the center, the left side support body10 is disposed at a negative domain of the Z axis and the right sidesupport body 20 is disposed at a positive domain of the Z axis, therebydetecting torque around the Z axis.

FIG. 35 is a front view which shows the annular deformation body 60 ofthe torque sensor according to the modification example (a view whenviewed from the right side support body 20). Also here, the V axis isdefined as a coordinate axis in which the X axis is rotatedcounterclockwise by 45 degrees on the XY plane, with the origin O givenas the center, and the W axis is defined as a coordinate axis in whichthe Y axis is rotated counterclockwise by 45 degrees, with the origin Ogiven as the center. As shown in the front view of FIG. 17, the annulardeformation body 50 according to the basic embodiment is such that foursets of the detection parts D1 to D4 and four sets of the coupling partsL1 to L4 are alternately disposed. As shown in the front view of FIG.35, the annular deformation body 60 according to the modificationexample is such that eight sets of detection parts D11 to D18 and eightsets of coupling parts L11 to L18 are alternately disposed.

FIG. 36 is a plan view which shows a disposition of the detection partsD11 to D18 and the coupling parts L11 to L18 which constitute theannular deformation body 60 shown in FIG. 35 (hatching is given forindicating a domain of the detection part and not for indicating a crosssection). As shown in the drawing, the annular deformation body 60 isconstituted by disposing the parts along the circular basic annularchannel R indicated by the alternate long and short dashed line in theorder of a first coupling part L11, a first detection part D11, a secondcoupling part L12, a second detection part D12, a third coupling partL13, a third detection part D13, a fourth coupling part L14, a fourthdetection part D14, a fifth coupling part L15, a fifth detection partD15, a sixth coupling part L16, a sixth detection part D16, a seventhcoupling part L17, a seventh detection part D17, an eighth coupling partL18 and an eighth detection part D18.

A basic structure of each of the detection parts D11 to D18 is similarto the basic structure of each of the detection parts D1 to D4 describedabove. For example, in FIG. 35, there is shown an example in which thefirst detection part D11 is constituted of a first deformation part 61,a second deformation part 62 and a displacement part 63. Here, the firstdeformation part 61, the second deformation part 62 and the displacementpart 63 are constituents similar to the first deformation part 51, thesecond deformation part 52 and the displacement part 53 of the detectionpart D shown in FIG. 20. And, a displacement electrode is formed at thedisplacement part 63 via an insulating layer.

Further, in the case of the annular deformation body 50 shown in FIG.15, two sites of the left side surface are connected to the left sidesupport body 10 by the left side connection members 11, 12, and twosites of the right side surface are connected to the right side supportbody 20 by the right side connection members 21, 22. In the case of theannular deformation body 60 shown in FIG. 35, four sites of the leftside surface are connected to the left side support body 10 by left sideconnection members 16, 17, 18, 19, and four sites of the right sidesurface are connected to the right side support body 20 by right sideconnection members 26, 27, 28, 29. Domains indicated by the broken linein FIG. 35 show projection images on the XY plane of domains to whichfour sets of the left side connection members 16, 17, 18, 19 areconnected and also projection images on the XY plane of domains to whichfour sets of the right side connection members 26, 27, 28, 29 areconnected.

FIG. 37 is a projection view on the XY plane which shows a dispositionof each of the detection points and each of the connection points of theannular deformation body 60 shown in FIG. 35 (a view when viewed fromthe right side support body 20: the annular deformation body 60 is shownonly by indicating a contour thereof). Also here, left side connectionpoints P16 to P19 are indicated by the white dot and right sideconnection points P26 to P29 are indicated by the black dot. As apparentfrom comparison between FIG. 36 and FIG. 37, a first left sideconnection point P16 is disposed at a first coupling part L11, a firstright side connection point P26 is disposed at a second coupling partL12, a second left side connection point P17 is disposed at a thirdcoupling part L13, a second right side connection point P27 is disposedat a fourth coupling part L14, a third left side connection point P18 isdisposed at a fifth coupling part L15, a third right side connectionpoint P28 is disposed at a sixth coupling part L16, a fourth left sideconnection point P19 is disposed at a seventh coupling part L17, and afourth right side connection point P29 is disposed at an eighth couplingpart L18.

In actuality, the first to the fourth left side connection points P16 toP19 are points which are defined on a side surface (the left sidesurface) of the annular deformation body 60 on a negative side of the Zaxis, and the first to the fourth right side connection points P26 toP29 are points which are defined on a side surface (the right sidesurface) of the annular deformation body 60 on a positive side of the Zaxis. Therefore, the individual connection points shown in FIG. 37 arepoints at which actual connection points are projected on the XY plane.

Consequently, where four straight lines X, V, Y, W passing through anintersection O with the rotation axis Z and intersecting at every45-degree angle difference with each other are drawn on the basic planeXY, orthogonal projection images of the first left side connection pointP16 and the third left side connection point P18 are disposed on a firststraight line X, orthogonal projection images of the first right sideconnection point P26 and the third right side connection point P28 aredisposed on a second straight line V, orthogonal projection images ofthe second left side connection point P17 and the fourth left sideconnection point P19 are disposed on a third straight line Y, andorthogonal projection images of the second right side connection pointP27 and the fourth right side connection point P29 are disposed on afourth straight line W.

Described in greater detail, where both side surfaces of the annulardeformation body 60 are projected on the XY plane to obtain orthogonalprojection images, a projection image of the first left side connectionpoint P16 is disposed on the positive X axis, a projection image of thesecond left side connection point P17 is disposed on the positive Yaxis, a projection image of the third left side connection point P18 isdisposed on the negative X axis, a projection image of the fourth leftside connection point P19 is disposed on the negative Y axis. And, aprojection image of the first right side connection point P26 isdisposed on the positive V axis, a projection image of the second rightside connection point P27 is disposed on the positive W axis, aprojection image of the third right side connection point P28 isdisposed on the negative V axis, and a projection image of the fourthright side connection point P29 is disposed on the negative W axis.

Then, the first left side connection member 16 connects the first leftside connection point P16 with the left side support body 10, the secondleft side connection member 17 connects the second left side connectionpoint P17 with the left side support body 10, the third left sideconnection member 18 connects the third left side connection point P18with the left side support body 10, and the fourth left side connectionmember 19 connects the fourth left side connection point P19 with theleft side support body 10. Further, the first right side connectionmember 26 connects the first right side connection point P26 with theright side support body 20, the second right side connection member 27connects the second right side connection point P27 with the right sidesupport body 20, the third right side connection member 28 connects thethird right side connection point P28 with the right side support body20, and the fourth right side connection member 29 connects the fourthright side connection point P29 with the right side support body 20.

As described above, the annular deformation body 60 is connected to theleft side support body 10 at four sites on the left side thereof andconnected to the right side support body 20 at four sites on the rightside thereof. Therefore, the annular deformation body 60 is quite firmlykept connected with the left side support body 10 and also quite firmlykept connected with the right side support body 20. As a result,rigidity of the torque sensor can be secured sufficiently where it isused at a joint of a robot arm, etc.

On the other hand, as shown in FIG. 37, eight detection points Q11 toQ18 are defined on the basic annular channel R. Specifically, where a VXaxis is defined at an intermediate position between the V axis and the Xaxis, a VY axis is defined at an intermediate position between the Vaxis and the Y axis, a WY axis is defined at an intermediate positionbetween the W axis and the Y axis, and a WX axis is defined at anintermediate position between the W axis and the X axis (the negativedirection), a first detection point Q11 is disposed at a positive domainof the VX axis, a second detection point Q12 is disposed at a positivedomain of the VY axis, a third detection point Q13 is disposed at apositive domain of the WY axis, a fourth detection point Q14 is disposedat a positive domain of the WX axis, a fifth detection point Q15 isdisposed at a negative domain of the VX axis, a sixth detection pointQ16 is disposed at a negative domain of the VY axis, a seventh detectionpoint Q17 is disposed at a negative domain of the WY axis, and an eighthdetection point Q18 is disposed at a negative domain of the WX axis.

Generally speaking, if an i-th detection point (1≤i≤8) is given as Qiand when a directional vector V_(ec) (θ) which gives counterclockwise anangle θ in relation to the positive direction of the X axis is definedon the XY plane, with the origin O given as a starting point, thedetection point Qi is positioned at an intersection between adirectional vector V_(ec) (π/8+(i−1)·π/4) and a basic annular channel R.For example, the first detection point Q11 is to be positioned at anintersection between a directional vector V_(ec) (π/8) which givescounterclockwise an angle of 22.5 degrees in relation to the positivedirection of the X axis and the basic annular channel R.

Eight sets of detection parts D11 to D18 are disposed at the respectivepositions of the detection points Q11 to Q18. Therefore, as a result, asshown in the front view of FIG. 35, the detection parts D11 to D18 aredisposed at intermediate positions between the X axis, the V axis, the Yaxis and the W axis. When torque (moment Mz) is exerted on the left sidesupport body 10 in a state that the right side support body 20 is fixed,clockwise or counterclockwise force is exerted on the left sideconnection members 16, 17, 18, 19 disposed on the X axis and the Y axisin a state that individual parts of the annular deformation body 60 arefixed by the right side connection members 26, 27, 28, 29 disposed onthe V axis and the W axis in FIG. 35. Therefore, a compressive force f1or an extension force f2 is exerted on each of the detection parts D11to D18, depending on a position thereof. The capacitive elements C11 toC18 are constituted respectively with displacement electrodes providedat displacement parts of the detection parts D11 to D18 and fixedelectrodes provided at opposing surfaces of the right side support body20, and these capacitive elements are changed in electrode distance,thus resulting in an increase or a decrease in capacitance values C11 toC18.

FIG. 38 is a table on the modification example which uses eight sets ofthe detection parts D11 to D18 shown in FIG. 35. And, the table shows anamount of fluctuation (an extent of increase or decrease) in capacitancevalue of each of the capacitive elements when force in the direction ofeach axis or moment around each axis is exerted on the left side supportbody 10 in a state that the right side support body 20 is fixed. Thefields of Mz are indicated by the enclosed thick lined frame, whichindicates that a force component to be originally detected by the torquesensor is moment Mz (torque around the Z axis).

In the table of FIG. 38 as well, in order to indicate an approximateabsolute value, three different reference symbols of “(+),” “+” and “++”are used for an increase in capacitance value, and three differentreference symbols of “(−),” “−” and “−−” are used for a decrease incapacitance value. “++” indicates a greater amount of fluctuation than“+,” and “(+)” indicates a smaller amount of fluctuation than “+.”Similarly, “−−” indicates a greater amount of fluctuation than “−” and“(−)” indicates a smaller amount of fluctuation than

When moment +Mz is exerted on the left side support body 10, in FIG. 35,there is applied force which allows positions of the left sideconnection members 16, 17, 8, 19 to move counterclockwise in a statethat positions of the right side connection members 26, 27, 28, 29 arefixed. Therefore, a compressive force f1 is exerted on the odd-numbereddetection parts D11, D13, D15 and D17, and an extension force f2 isexerted on the even-numbered detection parts D12, D14, D16 and D18.Therefore, the odd-numbered capacitive elements C11, C13, C15, C17 areincreased in capacitance value, while the even-numbered capacitiveelements C12, C14, C16, C18 are decreased in capacitance value. The rowof Mz in the table of FIG. 38 shows the above-described fluctuation.

With occurrence of the above described fluctuation taken into account,difference computation is performed on the basis of capacitance valuesof eight sets of the capacitive elements C11 to C18, thus making itpossible to calculate moment Mz (torque to be detected). FIG. 39 is atable which shows variations of formulae to be used in performing theabove difference computation. The arithmetic expression indicated inFIG. 39(a), “Mz=+C11−C12+C13−C14+C15−C16+C17−C18” is a formula forperforming difference computation which uses capacitance values of alleight sets of the capacitive elements C11 to C18. This is in practicethe most preferable arithmetic expression. On the other hand, thearithmetic expression shown in FIG. 39(b), “Mz=+C11−C12+C15−C16,” thearithmetic expression shown in FIG. 39(c), Mz=+C13−C14+C17−C18,” thearithmetic expression shown in FIG. 39(d), “Mz=−C12+C13−C16+C17” and thearithmetic expression shown in FIG. 39(e), “Mz=+C11−C14+C15−C18” are allformulae for performing difference computation using four sets ofcapacitance values selected from eight sets of the capacitance valuesC11 to C18. These are also able to calculate moment Mz (torque to bedetected) by means of difference computation.

Theoretically, any of the arithmetic expressions shown in FIG. 39(a) to(e) is adopted to set off other axis components (Fx, Fy, Fz, Mx, My),thus making it possible to remove errors resulting from interferencewith the other axis components, as described in Section 5-2. However, asdescribed in Section 7-1, in the table of FIG. 38 as well, an amount offluctuation of the component Mx or My, “++,” “−−” is larger than anamount of fluctuation of component Mz, “+,” “−.” Therefore, themodification example to which the auxiliary connection members describedin Section 7-1 are added is applied to a modification example which usesa total of eight sets of detection parts to be described here in Section7-2, thereby providing such an effect that reduces further errorsresulting from interference with the other axis components.

Specifically, the auxiliary connection member may be provided atpositions or in the vicinities of the left side connection points P16 toP19 (not necessarily all of them) indicated by the white dot in FIG. 37.As a matter of course, the auxiliary connection member is, as describedin Section 7-1, a member which connects between the right side surfaceof the annular deformation body 60 and the opposing surface of the rightside support body 20 and is able to play a role of “a supporting rod.”As with the example indicated by the broken line and the triangle markin FIG. 31, in the example shown in FIG. 37 as well, a part of theannular deformation body 60 (specifically, a part at which the X axisintersects with the Y axis) is expanded outward to provide a raisedpart, and the auxiliary connection member may be disposed at a positionof the raised part in place of the position indicated by the white dot.

FIG. 40 is a table which shows an amount of fluctuation (an extent ofincrease or decrease) in capacitance value of each of the capacitiveelements when force in the direction of each axis or moment around eachaxis is exerted on the left side support body 10 of the torque sensor inwhich the auxiliary connection member is also added to the modificationexample which uses eight sets of the detection parts shown in FIG. 35.In comparison with the table of FIG. 38, any of the fields of Fz, thefields of Mx and the fields of My are (+) or (−), showing reduction inerrors resulting from interference with the other axis components.

<7-3. Modification Example on Structure of Detection Part>

As a structure of the detection part D which is provided at the annulardeformation body 50 or 60 of the present invention, FIG. 19(a) shows thestructure which has the first plate-shaped piece 51, the secondplate-shaped piece 52 and the displacement part 53. In the case of theexample shown in this drawing, the first plate-shaped piece 51 and thesecond plate-shaped piece 52 are inclined to the normal line N and aninclination direction of the first plate-shaped piece 51 is also reverseto that of the second plate-shaped piece 52. As shown in FIG. 19(b),when the above-described constitution is adopted, the displacement part53 moves downward in the drawing upon exertion of a compressive force f1and the displacement part 53 moves upward in the drawing upon exertionof an extension force f2. Therefore, it is possible to detect thedirection and magnitude of exerted torque by referring to an increase ora decrease in capacitance value of the capacitive element C.

However, the structure of the detection part D usable in the presentinvention shall not be restricted to the structure shown in FIG. 19(a).FIG. 41 is a partial sectional view which shows a variation of thestructure of the detection part D.

The detection part DB shown in FIG. 41(a) is a detection part which isprovided at a part of an annular deformation body 50B and has a firstplate-shaped piece 51B, a second plate-shaped piece 52B, a displacementpart 53B, a first bridge part 54B and a second bridge part 55B. As shownin the drawing, any of the displacement part 53B, the first bridge part54B and the second bridge part 55B is a plate-shaped constituent whichis disposed so as to be parallel to the XY plane (the plane including abasic annular channel R). The first plate-shaped piece 51B and thesecond plate-shaped piece 52B are each a plate-shaped constituent whichis disposed so as to be orthogonal to the XY plane (so as to be parallelto the normal line N).

In the case of the detection part D shown in FIG. 19(a), the firstplate-shaped piece 51 and the second plate-shaped piece 52 are inclinedso as to be reverse in direction to each other. However, in the case ofthe detection part DB shown in FIG. 41(a), the first plate-shaped piece51B and the second plate-shaped piece 52B are kept parallel to eachother. Therefore, in the detection part DB, even upon exertion of acompressive force f1 or even upon exertion of an extension force f2, thefirst plate-shaped piece 51B and the second plate-shaped piece 52B areinclined to the normal line N, and in the both cases, the displacementpart 53B moves upward in the drawing. Thus, it is impossible to detectthe direction of exerted torque on the basis of an increase or adecrease in capacitance value of the capacitive element C but it ispossible to detect the magnitude of exerted torque by the detection partDB in an application where the direction of exerted torque has beendetermined.

The detection part DC shown in FIG. 41(b) is a detection part providedat a part of an annular deformation body 50C and has a firstplate-shaped piece 51C, a second plate-shaped piece 52C, a displacementpart 53C, a first bridge part 54C and a second bridge part 55C. As shownin the drawing, any of the displacement part 53C, the first bridge part54C and the second bridge part 55C is a plate-shaped constituentdisposed so as to be parallel to the XY plane (the plane including thebasic annular channel R). And, the first plate-shaped piece 51C and thesecond plate-shaped piece 52C are each a plate-shaped constituentdisposed in an inclined manner with respect to the normal line N so asto be opposite each other. However, the detection part DC is differentin an inclination mode from the detection part D shown in FIG. 19(a). Adistance between the plate-shaped pieces 51C and the 52C is increased toa greater extent as the displacement part 53C moves downward in thedrawing.

In the detection part DC, upon exertion of a compressive force f1, thedisplacement part 53C moves upward in the drawing, and upon exertion ofan extension force f2, the displacement part 53C moves downward in thedrawing, undergoing displacement reverse in direction to that of thedetection part D shown in FIG. 19(a). However, the detection part DC isable to detect the direction and magnitude of exerted torque on thebasis of an increase or a decrease in capacitance value of thecapacitive element C.

As a matter of course, various structures including the above can beadopted as the detection part D. In short, any structure may be adoptedas the detection part which can be used in the present invention, aslong as it is a structure in which the displacement part causesdisplacement to the right side support body 20 when a compressive forcef1 or an extension force f2 is exerted in a direction along the basicannular channel R.

<7-4. Modification Example which Uses Rectangular Annular DeformationBody>

The annular deformation body 50 shown in FIG. 17 and the annulardeformation body 60 shown in FIG. 35 are each a doughnut-shapedstructural body in which an inner circumferential contour and an outercircumferential contour are both circular. However, the annulardeformation body used in the present invention is not necessarilycircular but may be formed into any given structure in the shape of anellipse, a rectangle or a triangle. In short, any shaped annulardeformation body may be used as long as it is a structural body alongthe looped basic annular channel R.

FIG. 42 is a front view which shows a square-shaped annular deformationbody 60S which can be used in the present invention (when viewed fromthe side of the right side support body 20). The annular deformationbody 60S is a structural body in which inner and outer circumferentialcontours are both square and provided with an upper-side bridge part anda lower-side bridge part parallel to the X axis and a left-side bridgepart and a right-side bridge part parallel to the Y axis. Two sets ofdetection parts D12S, D13S are disposed at the upper-side bridge part,two sets of detection parts D14S, D15S are disposed at the left-sidebridge part, two sets of detection parts D16S, D17S are disposed at thelower-side bridge part, and two sets of detection parts D18S, D11S aredisposed at the right-side bridge part.

FIG. 43 is a plan view which shows a disposition of the detection partsand coupling parts of the square-shaped annular deformation body 60Sshown in FIG. 42 (hatching is given to indicate a domain of a detectionpart and not to indicate a cross section). As shown in the drawing, theannular deformation body 60S is constituted by disposing individualparts in the order of a first coupling part L11S, a first detection partD11S, a second coupling part L12S, a second detection part D12S, a thirdcoupling part L13S, a third detection part D13S, a fourth coupling partL14S, a fourth detection part D14S, a fifth coupling part L15S, a fifthdetection part D15S, a sixth coupling part L16S, a sixth detection partD16S, a seventh coupling part L17S, a seventh detection part D17S, aneighth coupling part L18S, and an eighth detection part D18S along asquare basic annular channel RS indicated by the alternate long andshort dashed line.

Each of the detection parts D11S to D18S is similar in basic structureto each of the detection parts D1 to D4 described above. For example, inFIG. 42, there is shown an example in which the first detection partD11S is constituted of a first deformation part 61S, a seconddeformation part 62S and a displacement part 63S. Here, the firstdeformation part 61S, the second deformation part 62S and thedisplacement part 63S are constituents respectively similar to the firstdeformation part 51, the second deformation part 52 and the displacementpart 53 of the detection part D shown in FIG. 20. A displacementelectrode is formed at the displacement part 63S via an insulatinglayer.

Further, in the case of the annular deformation body 60S shown in FIG.42, four sites of the left side surface thereof are connected to theleft side support body 10 by using left side connection members 16S,17S, 18S, 19S. And, four sites of the right side surface thereof areconnected to the right side support body 20 by using right sideconnection members 26S, 27S, 28S, 29S. The domains indicated by thebroken line in FIG. 42 show projection images on the XY plane of domainsto which four sets of the left side connection members 16S, 17S, 18S,19S are connected and projection images on the XY plane of domains towhich four sets of the right side connection members 26S, 27S, 28S, 29Sare connected.

FIG. 44 is a projection view on the XY plane which shows a dispositionof the individual detection points and the individual connection pointson the square-shaped annular deformation body 60S shown in FIG. 43 (whenviewed from the side of the right side support body 20: the annulardeformation body 60S is shown only by the contour). Also here, left sideconnection points P16 to P19 are indicated by the white dot, and rightside connection points P26 to P29 are indicated by the black dot. Asapparent from comparison between FIG. 43 and FIG. 44, the first leftside connection point P16 is disposed at a first coupling part L11S, thefirst right side connection point P26 is disposed at a second couplingpart L12S, the second left side connection point P17 is disposed at athird coupling part L13S, the second right side connection point P27 isdisposed at a fourth coupling part L14S, the third left side connectionpoint P18 is disposed at a fifth coupling part L15S, the third rightside connection point P28 is disposed at a sixth coupling part L16S, thefourth left side connection point P19 is disposed at a seventh couplingpart L17S, and the fourth right side connection point P29 is disposed atan eighth coupling part L18S.

On the other hand, as shown in FIG. 44, eight detection points Q11 toQ18 are defined on the basic annular channel RS. Each of the detectionpoints Q11 to Q18 is defined at an intermediate position between each ofthe left side connection points indicated by the white dot and each ofthe right side connection points adjacent thereto indicated by the blackdot. Eight sets of the detection parts D11S to D18S are disposedrespectively at the detection points Q11 to Q18 and, as a result, theseare disposed at the respective positions shown in the front view of FIG.42. Although a detailed description is omitted here, predeterminedcomputation is performed on the basis of capacitance values of eightsets of capacitive elements which are constituted by the eight detectionparts D11S to D18S provided on the square-shaped annular deformationbody 60S described above, by which it is possible to detect torqueexerted around the Z axis (moment Mz) in a state that errors resultingfrom interference with the other axis components are removed.

As a matter of course, the auxiliary connection member described inSection 7-1 are each provided at a position indicated by the white dotshown in FIG. 44. Thereby, as described by referring to the table ofFIG. 40, it is possible to more effectively remove errors resulting frominterference with the other axis components on the basis of exertion ofmoment Mx or My.

<7-5. Modification Example on the Number of Detection Parts>

In Section 4 to Section 6, a description has been given above of thebasic embodiment which uses four sets of the detection parts D1 to D4.In Section 7-2, a description has been given of the modification examplewhich uses eight sets of the detection parts D11 to D18. Further, in anyof these examples, a description has been given of the fact thatdifference detection can be performed to provide detection results fromwhich errors resulting from interference with the other axis componentsare removed. However, it is inevitable that the greater the number ofdetection parts, the higher the production cost. Therefore, wherepriority is given to reduction in production cost, some of the detectionparts in the examples described above can be omitted to reduce thenumber of detection parts.

As already described, difference detection can be performed to realizestable torque detection in which common-mode noise and zero-point driftare suppressed, contributing to setting off influences of expansion ofvarious parts due to temperatures to obtain a highly accurate detectionvalue. In order to perform the above-described difference detection,there may be used two sets of capacitive elements, one with anincreasing capacitance value and the other with a decreasing capacitancevalue.

Specifically, in the case of the basic embodiment described in Section 4to Section 6, of four sets of the capacitive elements C1 to C4 shown inthe table of FIG. 26, there are selected two sets of capacitive elementswhich are different in reference symbol in the fields of referencesymbols in the row of Mz, by which the thus selected two sets of thecapacitive elements can be only used to make difference detection. Forexample, only the capacitive elements C1, C2 may be used to detecttorque Mz on the basis of an arithmetic expression which is Mz=C2−C1.Further, in the case of the modification example described in Section7-2, about eight sets of the capacitive elements C11 to C18 shown in thetable of FIG. 38, two sets of capacitive elements which are different inreference symbol in the fields of reference symbols in the row of Mx areselected, thus making it possible to perform difference detection byusing only the thus selected two sets of the capacitive elements.

Therefore, in carrying out the present invention, the detection partsprovided on the annular deformation body are not necessarily used infour or eight sets but at least two sets of them could performdifference detection. Of course, only two sets of the detection partsare not able to obtain detection results from which errors resultingfrom interference with the other axis components are removed. Forexample, according to the table of FIG. 26, only the capacitive elementsC1 and C2 can be used to obtain a detection value of torque Mz on thebasis of the arithmetic expression of Mz=C2−C1. With reference to thefields of reference symbols in the row of Fx and the row of My in thetable, it can be understood that the computation result of “C2−C1”includes the components of Fx and My.

Therefore, in practice, in the case of such a sensor that is to be usedin an environment free of interference with the other axis components(for example, a sensor that is to be used by being housed in acylindrical tube, with the Z axis given as the central axis), theproduction cost thereof can be reduced by reducing the number ofdetection parts to two sets.

As a matter of course, it is possible to reduce the number of detectionparts to one set. Theoretically, one set of a detection part coulddetect the direction and magnitude of torque on the basis of an increaseor a decrease in capacitance value of one set of a capacitive element.However, only one set of the detection part is not able to performdifference detection, by which errors, etc., may occur due to a changein environmental temperatures, inevitably resulting in reduction indetection accuracy. Therefore, where high detection accuracy is not inpractice required but reduction in production cost is given the highestpriority, there may be provided a torque sensor which has only one setof a detection part.

<7-6. Modification Example on Left and Right Support Bodies>

In the examples described above, as shown in the example of FIG. 15, forexample, when viewed in the reference observation direction in which therotation axis Z is given as a horizontal line extending laterally, theleft side support body 10 is disposed so as to be adjacent to the leftside of the annular deformation body 50 and the right side support body20 is disposed so as to be adjacent to the right side of the annulardeformation body 50. In other words, one pair of the support bodies 10,20 are disposed on both left and right sides of the annular deformationbody 50. However, where one pair of the support bodies 10, 20 havefunctions to transmit torque to be detected to the annular deformationbody 50 for causing deformation and these are disposed so as to detectthe torque as a change in capacitance value of a capacitive element,these are not necessarily disposed in such a manner as to hold theannular deformation body 50 between both of them.

As described above, the pair of support bodies are not necessarilydisposed on the left side or on the right side of the annulardeformation body 50. Thus, in the following description, one of thesupport bodies is referred to as an exertion support body, while theother of the support bodies is referred to as a fixing support body. Theexertion support body corresponds to the left side support body 10described above, while the fixing support body corresponds to the rightside support body 20 described above. The fixing support body is asupport body which is made in a fixed state or made in a state that aload is applied upon detection of torque. In the case of the examplesdescribed above, this is a support body in which a fixed electrode isformed which constitutes a capacitive element C. On the other hand, theexertion support body has functions to apply torque to the annulardeformation body 50 where the fixing support body is in a fixed state orin a state that a load is applied thereto.

Of course, in the examples described above, for the sake of convenience,a description has been given of a case where there is detected torqueexerted on the left side support body 10 (the exertion support body) ina state that the right side support body 20 (the fixing support body) isfixed. In contrast, if there is detected torque exerted on the rightside support body 20 in a state that the left side support body 10 isfixed, a motion principle thereof is the same according to the law ofaction and reaction. Therefore, the above-described terms of theexertion support body and the fixing support body are only that, for thesake of convenience, on the assumption that torque exerted on the otheris detected in a state that one of the bodies is fixed, one of thebodies is referred to as the fixing support body and the other isreferred to as the exertion support body. If these are exchanged, noproblem is posed according to the principle of detection.

FIG. 45 is a side view which shows a basic structural part of amodification example in which an exertion support body 70 is disposedoutside an annular deformation body 50. For the sake of convenience ofillustration, the exertion support body 70 and exertion connectionmembers 71, 72 are shown as their cross sections, and other constituentsare shown as their side surfaces. As for detection parts, there areshown only outer circumferential surfaces of detection parts D2, D3which are positioned forward. This modification example is obtained byreplacing the left side support body 10 and the left side connectionmembers 11, 12 of the example shown in FIG. 16 by the exertion supportbody 70 and the exertion connection members 71, 72. Other constituentsare identical to those of the example shown in FIG. 16.

FIG. 46 is a front view in which a right side support body 20 is removedfrom the basic structural part shown in FIG. 45 and only the annulardeformation body 50 and the exertion support body 70 are viewed from theright side in FIG. 45. The exertion support body 70 is a circularannular structural body which is disposed so as to surround the annulardeformation body 50 from the outside thereof. As shown in FIG. 46, theannular deformation body 50 and the exertion support body 70 are bothdisposed in a concentric manner, with the Z axis given as the centralaxis. A first exertion connection member 71 is disposed at a positivedomain of the Y axis to connect an inner circumferential surface of theexertion support body 70 with an outer circumferential surface of theannular deformation body 50 (the outer circumferential surface of thecoupling part L2). Similarly, a second exertion connection member 72 isdisposed at a negative domain of the Y axis to connect an innercircumferential surface of the exertion support body 70 with an outercircumferential surface of the annular deformation body 50 (the outercircumferential surface of the coupling part L4).

Therefore, in the case of this modification example, a first exertionconnection point P71 is defined at a position at which the outercircumferential surface of the annular deformation body 50 intersectswith a positive domain of the Y axis, and a second exertion connectionpoint P72 is defined at a position at which the outer circumferentialsurface of the annular deformation body 50 intersects with a negativedomain of the Y axis. The first exertion connection member 71 hasfunctions to connect the first exertion connection point P71 with theinner circumferential surface of the exertion support body 70. And, thesecond exertion connection member 72 has functions to connect the secondexertion connection point P72 with the inner circumferential surface ofthe exertion support body 70.

As a matter of course, positions of the exertion connection points P71,P72 shall not be restricted to those on the Y axis shown in the drawing.These can be defined at any given position as long as, with regard tothe basic plane (XY plane), orthogonal projection images of the exertionconnection points P71, P72 and orthogonal projection images of thefixing connection points P21, P22 (the right side connection points P21,P22 shown in FIG. 18) are formed at mutually different positions. In thecase of the modification example shown in the drawing, the firstexertion connection point P71 can be defined at any given position onthe surface of the coupling part L2 (not necessarily on the outercircumferential surface). It will be sufficient that the first exertionconnection member 71 connects the first exertion connection point P71with the exertion support body 70. Similarly, the second exertionconnection point P72 can be defined at any given position on the surfaceof the coupling part L4 (not necessarily on the outer circumferentialsurface). It will be sufficient that the second exertion connectionmember 72 connects the second exertion connection point P72 with theexertion support body 70.

Since it is necessary to fix the fixed electrode E20 which constitutesthe capacitive element C, the right side support body 20 is required tobe disposed at a position adjacent to the right side of the annulardeformation body 50. Therefore, in the modification example shown inFIG. 45, the right side support body 20 and the fixing connectionmembers 21, 22 are identical in constitution to the right side supportbody 20 and the right side connection members 21, 22 shown in theexample of FIG. 16.

FIG. 47 is a side sectional view which shows a basic structural part ofa modification example in which an exertion support body 80 is disposedinside an annular deformation body 50 (indicating a cross section cutalong the YZ plane). This modification example is obtained by replacingthe exertion support body 70 and the exertion connection members 71, 72(each of which is disposed outside the annular deformation body 50) ofthe modification example shown in FIG. 45 by an exertion support body 80and exertion connection members 81, 82 (each of which is disposed insidethe annular deformation body 50). And, other constituents are identicalto those of the modification example shown in FIG. 45.

FIG. 48 is a front view in which a right side support body 20 is removedfrom the basic structural part 20 shown in FIG. 47 and only the annulardeformation body 50 and the exertion support body 80 are viewed from theright side in FIG. 47. The exertion support body 80 is a cylindricalstructural body which is disposed inside the annular deformation body50, and as shown in FIG. 48, the annular deformation body 50 and theexertion support body 80 are each disposed in a concentric manner, withthe Z axis given as the central axis. There may be used, as the exertionsupport body 80, a cylindrical structural body which forms athrough-opening part H80 in the interior thereof, in place of acylindrical structural body, if necessary.

A first exertion connection member 81 is disposed at a positive domainof the Y axis to connect an outer circumferential surface of theexertion support body 80 with an inner circumferential surface (theinner circumferential surface of the coupling part L2) of the annulardeformation body 50. Similarly, a second exertion connection member 82is disposed at a negative domain of the Y axis to connect the outercircumferential surface of the exertion support body 80 with the innercircumferential surface (the inner circumferential surface of thecoupling part L4) of the annular deformation body 50.

Therefore, in the case of this modification example, a first exertionconnection point P81 is defined at a position at which the innercircumferential surface of the annular deformation body 50 intersectswith a positive domain of the Y axis, and a second exertion connectionpoint P82 is defined at a position at which the inner circumferentialsurface of the annular deformation body 50 intersects with a negativedomain of the Y axis. The first exertion connection member 81 hasfunctions to connect the first exertion connection point P81 with theouter circumferential surface of the exertion support body 80. And, thesecond exertion connection member 82 has functions to connect the secondexertion connection point P82 with the outer circumferential surface ofthe exertion support body 80.

In this modification example as well, positions of the exertionconnection points P81, P82 are not restricted to the positions on the Yaxis as shown in the drawing. These can be defined in any given positionas long as, with regard to the basic plane (XY plane), orthogonalprojection images of the exertion connection points P81, P82 andorthogonal projection images of fixing connection points P21, P22 (theright side connection points P21, P22 shown in FIG. 18) are formed atmutually different positions. In the case of the modification exampleshown in the drawing, the first exertion connection point P81 can bedefined at any given position on the surface of the coupling part L2(not necessarily on the inner circumferential surface). It will besufficient that the first exertion connection member 81 connects thefirst exertion connection point P81 with the exertion support body 80.Similarly, the second exertion connection point P82 can be defined atany given position on the surface of the coupling part L4 (notnecessarily on the inner circumferential surface). It will be sufficientthat the second exertion connection member 82 connects the secondexertion connection point P82 with the exertion support body 80.

In this modification example as well, since it is necessary to fix thefixed electrode E20 which constitutes the capacitive element C, theright side support body 20 is required to be disposed at a positionadjacent to the right side of the annular deformation body 50.Therefore, in the modification example shown in FIG. 47, the right sidesupport body 20 and fixing connection members 21, 22 are identical inconstitution to the right side support body 20 and the right sideconnection members 21, 22 of the example shown in FIG. 16.

As a matter of course, the modification examples shown in FIG. 45 toFIG. 48 can be used in combination with the modification examplesdescribed in Section 7-1 to Section 7-5. For example, FIG. 49 is adrawing which shows an example in which the modification exampledescribed in Section 7-2 is combined with the modification example shownin FIG. 45 and FIG. 46, thereby showing a state that the annulardeformation body 60 shown in FIG. 35 is supported from outside by theexertion support body 70 (a front view when viewed in the rightdirection). As described already, the annular deformation body 60 isprovided with a total of eight sets of the detection parts D11 to D18and fixed to the right side support body 20 (the fixing support body) byfour sets of the right side connection members 26 to 29 (fixingconnection members) (in the drawing, each position is indicated by thebroken line).

On the other hand, the exertion support body 70 is a circular annularstructural body disposed so as to surround the annular deformation body60 from the outside thereof. As shown in FIG. 49, the annulardeformation body 60 and the exertion support body 70 are each disposedin a concentric manner, with the Z axis given as the central axis. Theseare connected together by four sets of exertion connection members 76 to79. Here, the first exertion connection member 76 is disposed at apositive domain of the X axis, the second exertion connection member 77is disposed at a positive domain of the Y axis, the third exertionconnection member 78 is disposed at a negative domain of the X axis, andthe fourth exertion connection member 79 is disposed at a negativedomain of the Y axis. Any of them connects the inner circumferentialsurface of the exertion support body 70 with the outer circumferentialsurface of the annular deformation body 60.

Therefore, in the case of the modification example shown in FIG. 49, afirst exertion connection point P76 is defined at a position at whichthe outer circumferential surface of the annular deformation body 60intersects with the positive domain of the X axis, a second exertionconnection point P77 is defined at a position at which the outercircumferential surface of the annular deformation body 60 intersectswith the positive domain of the Y axis, a third exertion connectionpoint P78 is defined at a position at which the outer circumferentialsurface of the annular deformation body 60 intersects with the negativedomain of the X axis, and a fourth exertion connection point P79 isdefined at a position at which the outer circumferential surface of theannular deformation body 60 intersects with the negative domain of the Yaxis.

In contrast, FIG. 50 is a drawing which shows an example in which themodification example described in Section 7-2 is combined with themodification examples shown in FIG. 47 and FIG. 48, showing a state thatthe annular deformation body 60 shown in FIG. 35 is supported frominside by the exertion support body 80 (the front view when viewed inthe right direction). In the case of the modification example as well,an annular deformation body 60 is provided with a total of eightdetection parts D11 to D18 and fixed to a right side support body 20 (afixing support body) by four sets of right side connection members 26 to29 (fixing connection members) (in the drawing, each position isindicated by the broken line).

On the other hand, an exertion support body 80 is a cylindricalstructural body disposed inside the annular deformation body 60 (as amatter of course, a circular structural body will do). As shown in FIG.50, the annular deformation body 60 and the exertion support body 80 areboth disposed in a concentric manner, with the Z axis given as thecentral axis, and these are connected together by four sets of exertionconnection members 86 to 89. Here, a first exertion connection member 86is disposed at a positive domain of the X axis, a second exertionconnection member 87 is disposed at a positive domain of the Y axis, athird exertion connection member 88 is disposed at a negative domain ofthe X axis, and a fourth exertion connection member 89 is disposed at anegative domain of the Y axis. And, any of them connects the outercircumferential surface of the exertion support body 80 with the innercircumferential surface of the annular deformation body 60.

Therefore, in the case of the modification example shown in FIG. 50, afirst exertion connection point P86 is defined at a position at whichthe inner circumferential surface of the annular deformation body 60intersects with the positive domain of the X axis, a second exertionconnection point P87 is defined at a position at which the innercircumferential surface of the annular deformation body 60 intersectswith the positive domain of the Y axis, a third exertion connectionpoint P88 is defined at a position at which the inner circumferentialsurface of the annular deformation body 60 intersects with the negativedomain of the X axis, and a fourth exertion connection point P89 isdefined at a position at which the inner circumferential surface of theannular deformation body 60 intersects with the negative domain of the Yaxis.

In other words, in the torque sensor which adopts the basic structuralpart according to the modification examples shown in FIG. 45 to FIG. 50,it will be sufficient that the exertion support body is disposed at aposition adjacent to the outside or the inside of the annulardeformation body, the fixing support body is disposed at a positionadjacent to the right side of the annular deformation body, exertionconnection points provided at a predetermined site of the annulardeformation body are connected with the exertion support body byexertion connection members, and fixing connection points provided at apredetermined site of the annular deformation body are connected withthe fixing support body by fixing connection members.

As shown in FIG. 15, in the basic structural part of the torque sensoraccording to the basic embodiment described in Section 4 and Section 5,the left side connection members 11, 12 play a role of connecting theleft side connection points P11, P12 defined on the left side surface ofthe annular deformation body 50 with the left side support body 10. Theright side connection members 21, 22 play a role of connecting the rightside connection points P21, P22 defined on the right side surface of theannular deformation body 50 with the right side support body 20.However, the left side connection points P11, P12 are not necessarilydefined on the left side surface of the annular deformation body 50 butmay be defined on an outer circumferential surface or an innercircumferential surface of the annular deformation body 50. Similarly,the right side connection points P21, P22 are not necessarily defined onthe right side surface of the annular deformation body 50 but may bedefined on an outer circumferential surface or an inner circumferentialsurface of the annular deformation body 50.

However, as with the basic embodiment described in Section 4 and Section5, where there is adopted such a constitution that the left side supportbody 10 and the right side support body 20 are provided on both left andright sides of the annular deformation body 50, the left side connectionpoints P11, P12 are defined on the left side surface of the annulardeformation body 50, and the right side connection points P21, P22 aredefined on the right side surface of the annular deformation body 50, bywhich the left side connection members 11, 12 and the right sideconnection members 21, 22 are made simple in structure (these may beconstituted simply with block-like members which connect between theleft and right side constituents). Therefore, in practice, it ispreferable that the left side connection points P11, P12 are defined onthe left side surface of the annular deformation body 50 and the rightside connection points P21, P22 are defined on the right side surface ofthe annular deformation body 50.

<7-7. Another Variation of Detection Part>

A description has been given above of the embodiment which uses thedetection part D having a unique structure shown in FIG. 19(a).Furthermore, in FIG. 41(a), (b), there are shown detection parts DB, DC,as a variation thereof. As a matter of course, various structural partscan be adopted as a detection part. As a detection part of the presentinvention, in short, any structural part can be adopted as long as it isstructured so as to cause displacement or deflection upon exertion of acompressive force f1 or an extension force f2 in a direction along thebasic annular channel R. Here, a description will be given of stillanother variation of a structure and a disposition of the detection partD.

In the case of the example shown in FIG. 19(a), the detection part Dwhich is disposed at a position of the detection point Q is constitutedof the first plate-shaped piece 51 and the second plate-shaped piece 52which will cause elastic deformation and the third plate-shaped piece53, both ends of which are supported by the plate-shaped pieces 51, 52.The third plate-shaped piece 53 functions as a displacement part. Here,when the normal line N orthogonal to the XY plane is provided at aposition of the detection point Q, the first plate-shaped piece 51 andthe second plate-shaped piece 52 are inclined to the normal line N, andalso the first plate-shaped piece 51 is reversed to the secondplate-shaped piece 52 in an inclination direction. Further, in a statethat no torque is exerted, an opposing surface of the third plate-shapedpiece 53 (the displacement part) is kept parallel to an opposing surfaceof the right side support body 20.

Here, when noted is a planar shape of the detection part described ineach of the examples shown in FIG. 17, FIG. 31, FIG. 35, FIG. 46, FIG.48, FIG. 49 and FIG. 50, any of projection images of the firstplate-shaped pieces 51, 61, the second plate-shaped pieces 52, 62 andthe third plate-shaped pieces 53, 63 on the XY plane is formed in a fanshape similar to a trapezoid. Contour lines on left and right sides ofthe projection image are those along the radius toward the origin O. Forexample, any of the planar shapes of the plate-shaped pieces 51, 52, 53which constitute the detection part D1 shown in FIG. 17 is formed in afan shape similar to a trapezoid. This is because the annulardeformation body 50 is formed in a circular annular shape, the detectionparts D1 to D4 are each designed so as to be in agreement with thecircular annular shape.

In contrast, in the example shown in FIG. 42, for example, any of theplanar shapes of the plate-shaped pieces 61S, 62S, 63S which constitutethe detection part D11S is rectangular. This is because the annulardeformation body 60S is formed in a square annular shape, the detectionparts D11S to D18S are each designed so as to be in agreement with thesquare annular shape.

In the examples described above, the planar shape of each of theplate-shaped pieces which constitute the detection part is designed tobe a fan-shaped or rectangular in agreement with the shape of theannular deformation body. However, the planar shape of each of theplate-shaped pieces is not necessarily formed so as to be differentdepending on a case, as described in the above example. For example, asshown in FIG. 17, even where the circular annular-shaped deformationbody 50 is adopted, each of the plate-shaped pieces 51, 52, 53 may bedesigned so as to be rectangular in planar shape. In the example shownin FIG. 17, each of the plate-shaped pieces 51, 52, 53 is formedrectangular in planar shape, as with each of the plate-shaped pieces61S, 62S, 63S shown in the example of FIG. 42. Thereby, where athree-dimensional structure of the detection part D is formed by cuttingprocessing or wire-cut processing, a simple step of driving processingtools in the same direction can be adopted, and this is preferable inmass-producing sensors. Further, in the embodiments described above,there is used the detection part D having a structure in which thedisplacement parts 53, 63 undergo displacement in the direction of the Zaxis. However, the displacement parts 53, 63 do not necessarily undergodisplacement in the direction of the Z axis.

FIG. 51 is a plan view (a view at the upper part) which shows an annulardeformation body 90 having a detection part, the direction of which ischanged, in place of the annular deformation body 50 of the embodimentshown in FIG. 15 and an exertion support body 70 which is disposedoutside thereof. FIG. 51 is also a side sectional view (a view at thelower part) in which a basic structural part which is constituted byadding a fixing support body 120 to them is cut along the XZ plane. Foursets of the detection parts D1 to D4 provided on the annular deformationbody 50 shown in FIG. 15 are replaced in the annular deformation body 90shown in FIG. 51 by four sets of detection parts D1′ to D4′. Here, abasic structure of each of the four sets of detection parts D1′ to D4′is similar to a structure of the detection part D shown in FIG. 19(a)but different in direction on the annular deformation body.

As apparent from the detection part D1′ in FIG. 51, the detection partD1′ is constituted of a first plate-shaped piece 91 and a secondplate-shaped piece 92 which cause elastic deformation and a thirdplate-shaped piece 93, the both ends of which are supported by theplate-shaped pieces 91, 92. The third plate-shaped piece 93 functions asa displacement part. Here, the plate-shaped pieces 91, 92, 93respectively correspond to the plate-shaped pieces 51, 52, 53 shown inFIG. 19(a) and are disposed so as to be different in direction inrelation to the annular deformation body.

That is, in four sets of the detection parts D1 to D4 provided on theannular deformation body 50 shown in FIG. 15, the displacement part 53is positioned on the right side of the annular deformation body 50, andthe right surface of the displacement part 53 opposes the left surfaceof the right side support body 20 (the right side support body). Incontrast, in four sets of the detection parts D1′ to D4′ provided on theannular deformation body 90 shown in FIG. 51, the displacement part 93is positioned outside the annular deformation body 90, and an outersurface of the displacement part 93 opposes an inner circumferentialsurface of the exertion support body 70.

In other words, four sets of the detection parts D1′ to D4′ shown inFIG. 51 are structured in such a manner that four sets of the detectionparts D1 to D4 shown in FIG. 15 are rotated by 90 degrees, with thebasic annular channel R given as the rotation axis. Therefore, when acompressive force f1 is exerted along the basic annular channel R, thedisplacement part 93 undergoes displacement outward (refer to FIG.19(b)), and when an extension force f2 is exerted along the basicannular channel R, the displacement part 93 undergoes displacementinward (refer to FIG. 19(c)).

As described above, in four sets of the detection parts D1 to D4provided on the annular deformation body 50 shown in FIG. 15, thedisplacement part 53 undergoes displacement in the direction of the Zaxis. On the other hand, in four sets of the detection parts D1′ to D4′provided on the annular deformation body 90 shown in FIG. 51, thedisplacement part 93 undergoes displacement in the radial direction of acircle drawn on the XY plane, with the origin O given as the center.Therefore, as shown in FIG. 51, a displacement electrode E90 is formedon an outer surface of the displacement part 93 and a fixed electrodeE70 is formed on an inner circumferential surface of the exertionsupport body 70 opposing thereto, thus making it possible to constitutea capacitive element C with a pair of electrodes E90, E70. Next, acapacitance value of the capacitive element C can be used as a parameterwhich indicates displacement of the displacement part 93 in the radialdirection.

In the case of the modification example shown in FIG. 51, fixingconnection members 121, 122 are disposed at positions along the Y axisand connected to the fixing support body 120. Exertion connectionmembers 73, 74 are disposed at positions along the X axis and connectedto the exertion support body 70. This is different in connection modefrom the example shown in FIG. 15. That is, in the case of the exampleshown in FIG. 15, the fixing connection members 21, 22 are disposed atpositions along the X axis and connected to the right side support body20. And, the exertion connection members 11, 12 are disposed atpositions along the Y axis and connected to the exertion support body10.

Therefore, four sets of capacitive elements C1′ to C4′ formed by foursets of the detection parts D1′ to D4′ shown in FIG. 51 are reverse inbehavior to four sets of the capacitive elements C1 to C4 formed by foursets of the detection parts D1 to D4 shown in FIG. 15. That is, thebehavior of the capacitive elements C1′ to C4′ of the modificationexample shown in FIG. 51 is such that a relationship of the f1 and thef2 in the fields of stress shown in FIG. 22 is reversed and referencesymbols in the fields of an amount of fluctuation are reversed.Therefore, an arithmetic expression for calculating torque Mz isexpressed by Mz=+C1−C2+C3−C4. However, as described above, this is dueto a slight change in connection mode and not an essential difference.

Further, in the example shown in FIG. 15, there is provided the annularright side support body 20 having the through-opening part H20 at thecenter, whereas in the modification example shown in FIG. 51(b), thereis provided a disk-shaped fixing support body 120 free of an openingpart. This is not an essential difference either. As described above, inthe example shown in FIG. 15, the through-opening part is provided onall of the three constituents 10, 20, 50. Therefore, any given axis canbe inserted through along the Z axis when such a necessity is raised.However, when such a necessity is not raised, as shown in the example ofFIG. 51(b), use of the disk-shaped fixing support body 120 will besufficient.

The modification example shown in FIG. 51 has the following twoimportant points. A first point is that where a capacitive element isused as a detection element, the capacitive element is not necessarilyrequired to change in electrode interval in the direction of the Z axis.The example shown in FIG. 51 is such that the capacitive element changesin electrode interval in the radial direction. As a matter of course,there may be used such a capacitive element, the electrode interval ofwhich will change in any direction other than the above direction.

Next, a second point is that where a capacitive element is used as adetection element, it is necessary to provide the displacement electrodeE90 at a detection part (that is, the annular deformation body).However, the fixed electrode E70 which opposes the displacementelectrode E90 is not necessarily provided at the fixing support body 120and may be provided at the exertion support body 70. In the individualembodiments described up to Section 7-6, any of the fixed electrodes isprovided on the fixing support body. In the case of the modificationexample shown in FIG. 51, however, the fixed electrode E70 is providednot on the fixing support body 120 but on an inner circumferentialsurface of the circular annular-shaped exertion support body 70. Here,the exertion support body 70 undergoes displacement by exertion oftorque, thus resulting in displacement of the fixed electrode E70.However, the displacement by exertion of torque occurs along the innercircumferential surface of the exertion support body 70. Therefore,there is no influence on the distance between the electrode of each ofthe capacitive elements C1′ to C4′ and there is no trouble in torquedetection.

<7-8. Modification Example which Uses Strain Gauge>

Still another mode of the detection part will be shown here and also adescription will be given of a modification example in which a straingauge is used as a detection element. A detection part DD shown in FIG.52(a) is a detection part which is provided at a part of an annulardeformation body 40. The detection part has a very simple structurecomposed of a single plate-shaped deformation part 41. In actuality, theabove-described detection part DD is disposed at a plurality of sites onan annular deformation body 40. In other words, the annular deformationbody 40 is a ring-shaped structural body in which a plurality ofplate-shaped deformation parts and a plurality of coupling parts L arealternately disposed.

The plate-shaped deformation part 41 is a constituent which causeselastic deformation by exertion of torque to be detected, and a platesurface thereof is disposed so as to be inclined to the XY plane (aplane including the basic annular channel R). As with the individualembodiments described above, where a capacitive element is used as adetection element, it is not preferable to adopt a simple structure suchas the detection part DD. However, where a strain gauge is used as adetection element, a simple structure such as the detection part DD issufficiently useful.

In the above-described embodiments, a capacitive element is used as adetection element for detecting elastic deformation occurring at thedetection part. In carrying out the present invention, however, thedetection element is not necessarily limited to a capacitive element. Ina modification example given below, a strain gauge which is fixed at aposition of the detection part causing elastic deformation is used as adetection element, and a circuit which outputs an electric signalindicating exerted torque on the basis of fluctuation in electricalresistance of the strain gauge is used as a detection circuit.

FIGS. 52(b) and (c) are each a partial sectional view which shows anelastic deformation mode of the plate-shaped deformation part 41 whichconstitutes the detection part DD shown in FIG. 52(a). FIG. 52(a) showsa state that no external force is exerted on the detection part DD. Uponexertion of an external force on the detection part DD, deflection shownin FIGS. 52(b) and (c) will occur at the plate-shaped deformation part41.

First, consideration is given to a case where the compressive force f1shown in FIG. 52(b) is exerted at a position of a detection point Q ofthe annular deformation body 40. In this case, the plate-shapeddeformation part 41 undergoes deflection, and stress indicated by “−” or“+” in the drawing occurs at individual parts of the surface thereof.Here, “+” indicates compression stress (that is, stress contractingalong the basic annular channel R), and “−” indicating extension stress(that is, stress expanding laterally in the drawing along the basicannular channel R). As shown in the drawing, stress occurring on thesurface of the plate-shaped deformation part 41 concentrates in thevicinity of an end of the plate-shaped deformation part 41 which isconnected with a coupling part L. On the other hand, where an extensionforce f2 is exerted on a position of the detection point Q, there isobtained stress distribution indicated by reference symbols opposite tothose in FIG. 52(b).

In contrast, FIG. 52(c) shows stress distribution occurring where forcein the longitudinal direction is exerted on an adjacent pair of couplingparts L. Specifically, the example shown in the drawing is to show thestress distribution obtained when a force f3 which is downward in thedrawing is exerted on the coupling part L on the left side, and a forcef4 which is upward in the drawing is exerted on the coupling part L onthe right side. In this case as well, the stress occurring on thesurface of the plate-shaped deformation part 41 concentrates in thevicinity of an end of the plate-shaped deformation part 41 which isconnected with the coupling part L. However, the sensor according to thepresent invention is a torque sensor which detects moment exerted aroundthe Z axis. Therefore, a force component to be detected is thecompressive force f1 shown in FIG. 52(b) or the extension force f2 whichis reversed thereto, and it is not necessary to detect the force f3 orthe force f4 shown in FIG. 52(c).

With consideration given to the above-described stress developingphenomenon, in order to detect elastic deformation occurring at thedetection part DD by using strain gauges by means of the detection partDD composed of the plate-shaped deformation part 41 shown in thedrawing, it is found that effective detection can be made by disposingindividual strain gauges on both surfaces of the plate-shapeddeformation part 41 in the vicinity of an end thereof which is connectedwith a coupling part L.

FIG. 53 covers a side view (FIG. (a)) and a top view (FIG. (b)) in whichthe strain gauge is used on the basis of the above consideration as adetection element for detecting elastic deformation occurring at thedetection part DD shown in FIG. 52(a). Where the annular deformationbody 40 is circular, the basic annular channel R is to constitute acircle. However, in FIG. 53(b), for the sake of convenience ofdescription, the basic annular channel R is partially indicated by thestraight line.

As shown in the drawing, in the plate-shaped deformation part 41 whichconstitutes the detection part DD, a first strain gauge r1 is attachedon a front face of the deformation part 41 in the vicinity of a firstconnection end thereof with a coupling part L on the left side, and asecond strain gauge r2 is attached on a rear face thereof. Similarly, athird strain gauge r3 is attached on a front face of the deformationpart 41 in the vicinity of a second connection end thereof with acoupling part L on the right side, and a fourth strain gauge r4 isattached on a rear face thereof.

FIG. 54 is a circuit diagram which shows a bridge circuit 108 foroutputting electric signals on the basis of detection results of foursets of the strain gauges r1 to r4 shown in FIG. 53. Specifically, thebridge circuit 108 is a circuit in which the first strain gauge r1 andthe fourth strain gauge r4 are given as a first opposite side, while thesecond strain gauge r2 and the third strain gauge r3 are given as asecond opposite side. The bridge circuit is actuated by application of apredetermined voltage from a bridge voltage source e. A detectioncircuit for detecting a bridge voltage generated between both outputterminals T1, T2 is provided on the bridge circuit 108, by which thebridge voltage can be used as a parameter which indicates an extent ofdeformation shown in FIG. 52(b) or an extent of deformation which isreverse thereto.

Therefore, for example, four sets of the detection parts D1 to D4 of theannular deformation body 50 shown in the example of FIG. 15 are replacedby the detection parts DD shown in FIG. 52(a) to constitute the annulardeformation body 40, and in the annular deformation body 40, four setsof the strain gauges r1 to r4 shown in FIG. 53 are disposed at each ofthe detection parts DD to constitute the bridge circuits 108 shown inFIG. 54. Thereby, bridge voltages of the individual bridge circuits 108can be used as parameters for indicating stress in the table of FIG. 22.Therefore, four sets of the bridge voltages are computed according tothe arithmetic expression shown in FIG. 22, thus making it possible toobtain a detection value of exerted torque as an electric signal.

<7-9. Essential Constituents of the Torque Sensor According to thePresent Invention>

Consequently, with consideration given to the basic embodiment andvarious modification examples described above, the torque sensoraccording to the present invention is essentially a torque sensor whichincludes the following individual constituents and detects torque arounda predetermined rotation axis (Z axis).

(1) An annular deformation body which extends along the basic annularchannel when a basic annular channel is defined so as to surround acircumference of a rotation axis on a basic plane (the XY plane)orthogonal to the rotation axis,

(2) An exertion support body which exerts torque on the annulardeformation body,

(3) A fixing support body which fixes the annular deformation body,

(4) An exertion connection member which connects an exertion connectionpoint provided at a predetermined site of the annular deformation bodywith the exertion support body,

(5) A fixing connection member which connects a fixing connection pointprovided at a predetermined site of the annular deformation body withthe fixing support body,

(6) A detection element for detecting elastic deformation occurring atthe annular deformation body, and

(7) A detection circuit which outputs, on the basis of detection resultsof the detection element, an electric signal indicating torque aroundthe rotation axis exerted on one of the exertion support body and of thefixing support body in a state that a load is applied to the other.

Here, the annular deformation body is provided with a detection partwhich is positioned at a detection point defined on the basic annularchannel and a coupling part which is connected to both ends of thedetection part. An exertion connection point and a fixing connectionpoint are disposed at the coupling part and an orthogonal projectionimage of the exertion connection point on the basic plane and anorthogonal projection image of the fixing connection point on the basicplane are formed at mutually different positions. Further, the detectionpart is provided with an elastic deformation structure part whichundergoes elastic deformation on the basis of exerted force uponexertion of force between the exertion connection point and the fixingconnection point. The detection element detects elastic deformationoccurring at the elastic deformation structure part. On the other hand,the coupling part may have some flexibility but the coupling partpreferably undergoes deformation to the minimum extent possible incausing effective deformation to the detection part by exerted torque.Therefore, in practice, it is preferable that the elastic deformationstructure part of the detection part is given as an elastic deformationbody which causes elastic deformation significantly detectable by thedetection element and the coupling part is given as a rigid body inwhich no significant deformation is detectable by detection sensitivityof the detection element.

Where a capacitive element is used as a detection element, it ispreferable to adopt the following unique structure as a detection part.That is, the detection part is provided with a first deformation partwhich causes elastic deformation by exertion of torque to be detected, asecond deformation part which causes elastic deformation by exertion oftorque to be detected, and a displacement part which causes displacementby elastic deformation of the first deformation part and the seconddeformation part. And, an external end of the first deformation part isconnected to a coupling part adjacent thereto, while an internal end ofthe first deformation part is connected to the displacement part, and anexternal end of the second deformation part is connected to a couplingpart adjacent thereto, while an internal end of the second deformationpart is connected to the displacement part.

Further, the capacitive element which constitutes the detection elementmay be constituted of a displacement electrode fixed at a predeterminedsite of the detection part and a fixed electrode fixed at a position ofthe exertion support body or the fixing support body which opposesdisplacement electrode. Here, it will be sufficient that thedisplacement electrode is disposed at a position which causesdisplacement to the fixed electrode on the basis of elastic deformationoccurring at the detection part, and the detection circuit outputs anelectric signal indicating exerted torque on the basis of fluctuation incapacitance value of the capacitive element.

It is preferable that when viewed from a reference observation directionat which the rotation axis gives a horizontal line extending laterally,the exertion support body is disposed at a position adjacent to the leftside of the annular deformation body, at a position adjacent to theoutside of the annular deformation body or at a position adjacent to theinside of the annular deformation body. It is preferable that whenviewed from the reference observation direction, the fixing support bodyis disposed at a position adjacent to the right side of the annulardeformation body. In this case, the capacitive element can beconstituted of a displacement electrode which is fixed at apredetermined site on the right side surface of the annular deformationbody and a fixed electrode which is fixed at a position of the fixingsupport body which opposes the displacement electrode. Further, thedisplacement electrode may be fixed at a position of the displacementpart which opposes the fixing support body.

INDUSTRIAL APPLICABILITY

The torque sensor according to the present invention can be used formeasuring torque in various types of industrial machines by takingadvantage of being small in size, high in rigidity and capable ofrealizing high production efficiency. In particular, in an industrialmachine in which a robot arm is used to perform automatic assembly, thesensor is optimally used in an application where it is incorporated intoa joint part of the arm, thereby monitoring and controlling forceoccurring at the leading end of the arm.

What is claimed is:
 1. A torque sensor which detects torque around a predetermined rotation axis, the torque sensor comprising: an annular deformation body disposed so as to surround a circumference of the rotation axis, the annular deformation body undergoing elastic deformation by exertion of torque; an exertion support body provided on one side in a direction along the rotation axis, the exertion support body exerting the torque to the annular deformation body; a fixing support body provided on an other side in a direction along the rotation axis, the fixing support body fixing the annular deformation body; and a detection circuit which outputs electric signals indicating torque around the rotation axis; wherein the annular deformation body has four coupling parts, and four detection parts positioned between two coupling parts which are adjacent in the circumferential direction of the annular deformation body, the four detection parts undergoing elastic deformation by exertion of torque, the four detection parts each are formed in a convex shape on one side in a direction along the rotation axis and are formed in a concave shape on the other side in a direction along the rotation axis, the detection circuit outputs the electric signals on the basis of elastic deformation undergone to the four detection parts of the annular deformation body.
 2. The torque sensor according to claim 1, further comprising: a first side connection member which connects the annular deformation body with the exertion support body; and a second side connection member which connects the annular deformation body with the fixing support body.
 3. The torque sensor according to claim 2, wherein two coupling parts of the annular deformation body are connected with the exertion support body via two first side connection members, and the other two coupling parts of the annular deformation body are connected with the fixing support body via two second side connection members.
 4. The torque sensor according to claim 3, wherein the first connection member and the second connection member are disposed alternately in the circumferential direction of the annular deformation body.
 5. The torque sensor according to claim 2, wherein the first connection member and the second connection member are formed at mutually different positions when viewed in a direction along the rotation axis.
 6. The torque sensor according to claim 1, wherein the detection parts each are formed in a convex shape on the side of the fixing support body and are formed in a convex shape on the side of the exertion support body.
 7. The torque sensor according to claim 1, further comprising: a capacitive element having a displacement electrode provided to the detection part, the displacement electrode opposing the fixing support body, and a fixed electrode provided to the fixing support body, the fixed electrode opposing the displacement electrode, wherein the detection circuit outputs the electric signals on basis of a fluctuation in capacitance value of the capacitive element. 